Talk:Electron diffraction/Archive 1

Complete overhaul needed
This article needs to be reworked quite a bit. Not only is it a stub, but some of the statements made are simply wrong. For example: "The technique is only used on crystal samples..." (no, it is also used for amorphous solids and gas molecules) and "The electrons are scattered by interaction with the positively charged atomic nuclei." (no, the electrons are scattered by both the nuclei and electrons surrounding the atom core.)

Perhaps we should try to outline a new article? A first draft could be something like this:


 * Section: Wave-nature of electrons, link to article on interference of waves, link to article on general diffraction. Formula for wavelength of electrons as function of accelerating voltage. How are electrons scattered? Differences and similarities with photons (X-ray) and neutrons.


 * Section: how is electron diffraction used in crystal structure determination? In studies of amorphous solids? In studies of gas molecules? An alternative would be to rewrite the electron crystallography article (probably better, and should probably be done anyway).


 * Section: Geometry of electron diffraction in transmission


 * Section: Geometry of electron diffraction in backscattering


 * Section: Geometry of gas-electron diffraction

My experience is almost exclusively with electron diffraction in TEM and I'm going to need some help with the structuring and writing of this article!

oysteinp

First sketch
(October 19 2005 (oysteinp), modified October 20 (oysteinp), October 23 (oysteinp))

Could this work as a start?

Electron diffraction is a technique used to study matter by firing electrons at a sample and observing the resulting interference pattern. This phenomenon occurs due to the wave-particle duality, which states that a particle of matter (in this case the incident electron) just as well can be described as a wave. The electron is then diffracted in a similar fashion as classical waves such as sound or waves in water. This technique is similar to X-ray diffraction and neutron diffraction.

Electron diffraction is most frequently used in solid state physics and chemistry to study the crystal structure of solids. The periodic structure of a crystalline solid acts as a diffraction grating, scattering the electrons in a predictable manner. Working back from the observed diffraction pattern, it may be possible to deduce the crystal structure giving rise to that particular pattern. However, the technique is limited by the phase problem.

Apart from the study of crystals, electron diffraction is also a useful technique to study the short range order of amorphous solids, and the geometry of gaseous molecules.

Theory The wavelength of an electron is given by the de Broglie equation


 * $$\lambda = \frac{h}{p}$$

Here $$h$$ is Planck's constant, $$p$$ the momentum of the electron and $$m_0$$ its mass. The electrons are accelerated in an electric potential $$U$$ to the desired velocity:


 * $$v=\sqrt{\frac{2eU}{m_0}}$$

The electron wavelength is then given by:


 * $$\lambda=\frac{h}{p}=\frac{h}{m_0v}=\frac{h}{\sqrt{2m_0eU}}$$

However, in an electron microscope, the accelerating potential is usually several thousand volts causing the electron to travel at an appreciable fraction of the speed of light. An SEM may typically operate at an accelerating potential of 10.000 volts (10 kV) giving an electron velocity approximately 20% of the speed of light, while a typical TEM can operate at 200 kV raising the electron velocity to 70% the speed of light. We therefore need to take relativistic effects into account. It can be shown that the electron wavelength is then modified according to:


 * $$ \lambda = \frac{h}{\sqrt{2m_0eU}}\frac{1}{\sqrt{1+\frac{eU}{2mc^2}}}$$

We recognize the first term in this final expression as the non-relativistc expression derived above, while the last term is a relativistic correction factor. The wavelength of the electrons in a 10 kV SEM is then 12.3 x 10-12 m (12.3 pm) while in a 200 kV TEM the wavelength is 2.5 pm. In comparison the wavelength of X-rays usually used in X-ray diffraction is in the order of 100 pm (Cu k&alpha;: &lambda;=154 pm).


 * How are electrons scattered?
 * Differences and similarities with photons (X-ray) and neutrons.

Electron diffraction in the TEM

Electron diffraction of solids is usually performed in a Transmission Electron Microscope (TEM) where the electrons pass through a thin film of the material to be studied. The resulting diffraction pattern is then observed on a fluorescent screen or recorded on photographic film or a CCD camera. In the TEM, electron diffraction can be combined with a range of other techniques such as chemical analysis of the sample composition through energy-dispersive X-ray spectroscopy, direct imaging of the sample, including high resolution imaging of the crystal lattice, electron energy loss spectroscopy, and electron holography.

Geometry of electron diffraction in backscattering

Geometry of gas-electron diffraction

TEM-sentric
(23 October 2005, oysteinp) The article sketch I've posted above is becoming a little TEM-sentric. I'm sure there are lots of people out there that could add info om other forms of electron diffraction!


 * Why don't you just edit the article directly? You seem to know what you are talking about, don't be timid.  linas 06:58, 22 November 2005 (UTC)


 * Well, ok. I just thought it would be a good idea to discuss the content of the article :) But anyway: I've updated parts of the article. I'll work some more on it later. O. Prytz 21:09, 22 November 2005 (UTC)


 * For highly contentious articles, where many people are arguing over many things, that would be a very good, and polite, thing to do. This article, by contrast, suffers from neglect: no one is bothering much to edit it, and so there won't be much of a discussion, either. As long as you are ot adding patent non-sense, you'll have free reign. linas 00:12, 23 November 2005 (UTC)


 * I've written a bit more in the section on electron interation with matter, it's mostly a comparison of the different forms of interaction applicable to electrons vs. neutrons vs. X-rays. Could anyone have a look at this? I'm a bit uncertain about the details of this section and it would be good if someone could check the validity of the statements. O. Prytz 20:44, 6 December 2005 (UTC)
 * Done. Only the strong interaction counted for the nuclear force. I simplified the x-ray sentance. linas 04:55, 7 December 2005 (UTC)

I've added a section on electron diffraction in a TEM, a couple of figures and a reference. O. Prytz 14:45, 18 December 2005 (UTC)

New section
I've added a new section on the intensity of diffracted electron beams. It's not quite done yet. But the real question is really: how detailed should a Wikipedia article be? I mean: you could write a textbook if you like, but is that really appropriate?O. Prytz 13:05, 21 December 2005 (UTC)

I've fleshed out the Electron diffraction in TEM section a bit with a discussion of the benefits of this technique. I'll add a section on limitations later. Once againg I'm worried that the article may become a little too detailed and focused on TEM. Furthermore, maybe some of the content should be moved to the electron crystallography article (which really needs some work). O. Prytz 10:13, 31 December 2005 (UTC)

Done for now
Ok, I finished the section on limitations, but I'm afraid it's prettey POV so please have a look and rewrite/delete anything not belonging in an encyclopedia. I'll be adding some refrences to the article sooner or later... I'm still a bit worried that the article gives undue weight to electron diffraction in TEM. I might eventually move some of the content to electron crystallography which needs a bit of work. O. Prytz 19:20, 2 January 2006 (UTC)


 * Thanks! For the most part, it looks pretty good. You might also consider starting a new article electron diffraction in TEM, maybe. Or maybe nt. Eithre way, thanks. linas 21:09, 3 January 2006 (UTC)


 * Hm...that might be a good idea, although I think I'll wait until I've had a go at electron crystallography. O. Prytz 20:31, 4 January 2006 (UTC)

TEM centric
It's TEM centric because electron diffraction can be done on most any TEM, while it's not often done on an SEM. Why is the wavelength of the electron in an SEM so prominent and first when electron diffraction in an SEM is hardly touched upon? The order should be changed to reflect that the article includes extensive information about TEM electron diffraction, not SEM. --Blechnic (talk) 06:44, 28 May 2008 (UTC)

Assessment comment
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Article rating after substantial transform
Dear fellow Wikipedians,

the article has undergone a substantial transform in recent weeks (before and after) and I hope its rating became out-dated. If I understand it well, the rating can only be changed manually. If you agree the B is out-dated, could you please help me with changing it appropriately?

Similarly, there is an article about Selected area diffraction which I hope is not a Stub any more and another one about CrysTBox which has not been rated at all.

Thank you very much for your help.

Klingm01 (talk) 18:07, 7 March 2022 (UTC)

This article needs major work
This article, at least in it's current form, contains major errors of science. There are also some grammatical issues, although these are less severe Ldm1954 (talk) 11:18, 18 January 2023 (UTC)


 * Please fix it and include references for your additions / corrections. Regards, Ariconte (talk) 20:27, 18 January 2023 (UTC)


 * Thank you for your willingness to improve the article. However, deleting the whole Theory section (incl. all images, tables and formulas) is definitely not the best way. I'm not saying the section is perfect, but formulas and tables taken from the literature (see the references) are definitely not scientifically wrong neither are images showing the relation between spot and ring diffraction or what Kikuchi lines are. I hope that gradual edits (like those you have yourself made in this very section before deleting it) are much better way to improve the article. --Klingm01 (talk) 12:22, 4 February 2023 (UTC)

As someone who has taught the topic for decades, and extensively published I will tell you the section is awful, and misleading:

1. The non-relativistic wavelength form is never used.

2. The relativistic form is incorrect, as an effective mass is used to cancel some terms (see Hirsch et al or Peng, Dudarev & Whelan).

3. The statements/equations about kinematical theory are completely wrong -- there is a |sin(pi*t*sz)/(pi*sz)|**2 missing.

4. The "effects of crystallinity" is misleading, for instance double diffraction is ignored

5. As written the Kikuchi line section does not belong in this section. To do the theory properly Bloch waves have to be introduced first, which would be a large digression.

6 The gas phase section is also not theory.

While I understand that you want to give people a simple explanation so they can use simple codes, that takes knowledge backwards. The whole theory section must be removed. Electron diffraction is not simple.

Ldm1954 (talk) 11:22, 7 February 2023 (UTC)

Please, stop vandalizing the article
Lets's be minimalistic. Dear Ldm1954, feel free to continue with personal offenses and humiliations, feel free to improve the article, but please stop vandalizing it. After your edits, there are errors, empty sections, references to removed images, not mentioning the content. Klingm01 (talk) 14:58, 7 February 2023 (UTC)


 * The prior version would fail any decent TEM class at a strong university. Sorry, but that is reality. It is not "personal offenses", this is scientific rigor.
 * The current version is adequate, although I would still only give it a B-. I have to go and teach TEM, and will add more references later and further clarifications -- they are needed. Ldm1954 (talk) 16:06, 7 February 2023 (UTC)

Unsourced comments added
User:Ldm1954 has made a large number of unsourced edits, the user still doesn’t seem to understand how Wikipedia works. Adding comments here  with no sources. Theroadislong (talk) 18:56, 26 February 2023 (UTC)


 * The statement by Theroadislong is inaccurate. The relevant information is within a sentence or less of every statement that was added. Everything has stated sources.
 * User:Theroadislong, an apology would be appropriate.
 * Ldm1954 (talk) 19:16, 26 February 2023 (UTC)
 * Adding content AFTER a source is not how we do it, if the edit was covered by a previous source then the source should have been repeated. Theroadislong (talk) 21:15, 26 February 2023 (UTC)
 * User:Theroadislong the source was in the sentence before or the same paragraph, and clearly indicated. Please admit error. Ldm1954 (talk) 21:28, 26 February 2023 (UTC)

Ldm1954, do stop vandalizing the article
Dear Ldm1954, your expertise is most welcome. Instead of using it to disparage others and their contributions, please use it to improve the article. As mentioned before, the article is not necessarily perfect, but this does not mean, you can freely remove its substantial parts without providing better alternative.

Repeated removal of substantial content and claims of incorrect information
Above, you claim the "relativistic form is incorrect" and you say
 * "While I understand that you want to give people a simple explanation so they can use simple codes, that takes knowledge backwards. The whole theory section must be removed. Electron diffraction is not simple."

You have removed all the formulas claiming they were wrong and too simple. What have you left there instead? Nothing. Your repeated removal of Theory section leaves an impression that there is no theory behind the diffraction. This is what "takes knowledge backwards".

Moreover, you claim the relativistic wavelength formula and/or table to be incorrect. I have just checked the formula in the article and it equals to the one stated in Prof. Kirkland's book (see the references). If there is a mistake, please fix it in the article and inform Prof. Kirkland accordingly. If there is a mistake in the wavelength table, please tell us where. Carter&Williams, Karlík, de Graef - I have just checked their books and they all state exactly the same values you have deleted for being incorrect.

Article structure
The structure of the article had its purpose:
 * 1) History
 * 2) Theory - Non-relativistic, relativistic, material structure (singe/poly-crystal) etc.
 * 3) Applications - TEM (SAED, CBED etc.), SEM, Gases

This structure guided the reader from the History (from the first experiments up to de Brogile), then via the Theory (the reader could read the de Brogie's formula mentioned in the history, see its place in theory, via non-relativistic to the relativistic etc.), showing the impact of material structure on the diffractogram (single- vs. poly-crystal). The the Applications decribed TEM (it's importance from ED point, the beam and image formation, and individual experimental techniquies like SAED or CBED etc.), followed by SEM and gases.

As you know, the strengths and traps of the diffraction imaging originate from the fact, that the image is formed by so many factors at once - if we stay very simple, it's material structure, beam parameters and detectors. Please note here, that the original structure kept those factors separated instead of mixing them all together. This is crucial for understanding the influence of the individual aspects on the resulting diffraction.

Please note also, that the structure allowed the article to be read in whole (with a continuous flow and gradual information develpment) as well as in parts (individual subsections as self-supporting as possible).

After you "rationalized" the structure we have:
 * 1) History
 * 2) Types of electron diffraction

In the giant, unstructured section called Types of electron diffraction, you put together different instrument, phenomena or techniques with no respect to their functional or causal relations. At the same level in one single section, you mix together This looks as if the Scanning electron microscope shared the category and level with Kikuchi lines. This is extremely confusing. Of course, experts can orient themselves in this chaos, but beginners or cross-disciplinary people will be lost and confused. And this is encyclopedia - it should be readable for a broader audience.
 * experimental instruments (TEM, SEM, RHEED)
 * experimental techniques (CBED, 4D STEM, Precession etc.)
 * material structure (singe- vs. poly-crystalline samples)
 * general information specific to TEM (formation of image in TEM)
 * theory (double diffraction)
 * diffractogram features (Kikuchi lines)

Summary
These are just the major areas of arguments qualifying your activities as vandalism. I am not mentioning particularities like that you should prepare your edits in your sandbox instead of continuously editing the article visited by the readers meanwhile or that the non-realistic wavelength, which is mentioned in all relevant books, is relevant here, it allows to bridge the History and Theory and it's extent is proportional.

Please, do not repeat your vandalizing activity. As mentioned repeatedly, you are welcome to improve the articles. Try to focus on smaller, gradual changes. This does not mean, however, removing each Theory subsection individually (12:23, 7 February 2023‎ and later) instead of removing it at once (19:13, 2 February 2023). It means correcting particular mistakes as you spot them and can prove them. Before more substantial edits, feel free to contact the original authors or discuss them here on the talk page.

Your knowledge is needed, but use it constructively.

Klingm01 (talk) 12:56, 8 February 2023 (UTC)

Reactions

 * I will give you a hint, have a look at https://scholar.google.com/citations?user=zmHhI9gAAAAJ
 * Also, please say hello for me to Marianna, and ask if I will see her at IMC20 in September. Ldm1954 (talk) 16:01, 8 February 2023 (UTC)

I posted this on my talk page, I will repeat it here:

I am afraid that you have misunderstood. The full formulation for the energy and mass is standard and can be found in main sources such as HHPNW & JMC. Scientific rigor says cite the key early papers/books, not later ones. For instance from my class notes (you will find it elsewhere as well):

"The total energy is

Et2 = c2p2 +mo2c4

where mo is the rest mass of the electron, c the speed of light and Et is the sum of the rest energy and the kinetic energy of the electron, i.e.

Et = eE + moc2

The relativistically corrected mass to use is

m = mo + eE/2c2

(this is not the true mass of the electron, which is m0+eE/c2, but instead a value used to eliminate the relativistic terms)."

There is no real reason to go into this in the page, or the original Archie Howie explanation of how to reduce the Klein-Gordon/Dirac to the Schroedinger that is normally used in multislice/Bloch waves. (I intend to add selected refs)

For reference Marc's theory is strong, Earle's is good on multislice although I prefer the original work of Mike O'Keefe. I learnt a lot of my multislice theory from Mike O'Keefe over tea breaks back when my hair was black. Ldm1954 (talk) 15:20, 8 February 2023 (UTC) Ldm1954 (talk) 15:28, 8 February 2023 (UTC)


 * You're avoiding the answer because you took on yourself a very difficult task. Showing incorrectness of something which is correct is quite difficult.
 * You're standing alone against all these heavy weights of electron crystallography: Kirkland, Egerton , Carter&Williams , De Graef ... how many names do you need?


 * Let me remind you your own words: "Self criticism is an art not many are qualified to practice", Joyce Carol Oates
 * Klingm01 (talk) 16:37, 8 February 2023 (UTC)
 * To repeat, your formulation was incorrect.
 * The equations in those texts are almost certainly right.
 * However, the wavelength is not theory, and what was there was very much not kinematical. There is certainly no place in this section for the full Green's function derivation, e.g. http://www.numis.northwestern.edu/460/Notes/kinematical.docx or Hirsch et al. Ldm1954 (talk) 16:45, 8 February 2023 (UTC)
 * "Also, please say hello for me to..."
 * ...OK so now you're even threatening me with my boss. OK... Klingm01 (talk) 16:46, 8 February 2023 (UTC)
 * When I said "say hello" that is what I meant.
 * N.B., my identity is somewhat obvious and I just edited my home page. Ldm1954 (talk) 16:57, 8 February 2023 (UTC)
 * Ooops! The whole theory section is gone! That was the only place in the whole English Wikipedia that stated it at that level of detail, and I miss it. As far I can say, it was fully correct once contrasted all my available sources. I can't understand Ldm1954 when he says: However, the wavelength is not theory[...] (???) For sure it was theory, and it was only theory since De Broglie to Davisson. And it was non-relativistic at first. Once confirmed, it saw a quick development, of course. I agree with Klingm01's original vision for the article, as it was it was a perfect starting point to everyone interested on such development's history.
 * And it is a very interesting case in history of physics, one of the few where correct theories aforehead facts. Electromagnetic theory by Maxwell predicted electromagnetic waves produced by Hertz. Mass-energy equivalence theory by Einstein ultimately lead to nuclear power plants and weapons. And we all here know De Broglie anticipated electron microscopy (to be succint). Will you, Ldm1954, mutilate those "dated theories" in the corresponding articles? Then you can delete all Ptolomy related articles as well. Even Kepler's and Newton's formulations are all outdated by today's knowledge. Strip away them all from Wikipedia!
 * But I'm surprised the most with your notes: The relativistically corrected mass to use is m &equals;m0 + eE/2c2 (this is not the true mass of the electron, which is m0+eE/c2, but instead a value used to eliminate the relativistic terms). How you derived this? I assume eE = m/c2 – m0/c2 here, as per Et = eE + m0c2, so, Where that "corrected mass" came from? I've never heard on this, although it means nothing, of course, Wikipedia is meant to teach people about things like this, and I want to learn the more. And, How that "corrected mass" influences the wavelength? By using non-relativistic De Broglie, maybe, as that value "elimitate relativistic terms"?
 * Please, can some editor re-state the whole theory section as it prevously was? And then, may Ldm1954 or whoever extend it with appropriate material to explain about "corrected mass", and how it is used to compute wavelength. Thank you. 37.134.90.176 (talk) 08:43, 13 February 2023 (UTC)
 * For completeness, the relevant references and explanation are now included. The original Bethe paper in 1928 was non-relativistic, based upon Scroedinger's equation. The paper by Fujiwara in 1961 & the note by Howie in 1962 are the standard references on how relativistic diffraction is converted to non-relativistic using an effective mass -- the form is in the revised page. All of the hundreds of papers on swift electron diffraction use this fact, although it is very rarely mentioned; the Fujiwara paper has been, according to Google Scholar, only cited 176 times. Ldm1954 (talk) 14:33, 15 February 2023 (UTC)
 * You, Ldm1954, do not state the units for k wavevector. As per "The wavelength of the electrons is 1/k", the reader must to deduce by him/herself k is given in m–1. Also, you do not say what eE stands for. As it is spelt, it seems it is the product of elementary charge e, which is mentioned (or even the e number as per the exponential function also mentioned) and some energy E, which is quite confusing to the reader.
 * But eE (or better, Ee here, for "electron energy") comes from the difference of Et, "total energy", minus E0, or energy equivalent of the electron rest mass m0, that is, E0 = m0c2. So, Ee = Et – E0, as per your notes Et = Ee + m0c2, then Et = Ee + E0. Right?
 * Well. From your notes again, Et2 = c2p2 + m02c4, which is OK (c·p is given in Joules). Then, Et2 = c2p2 + E02. As E0 and c are constant (as m0 is), the variable here is p, the kinetic momentum of the electron as a particle of a given mass. The momentum is function of velocity v, so that mass must have been accelerated to attain that velocity. How the electron has been accelerated, in first place?
 * Of the many ways an electron can be accelerated, De Broglie choose the energy the electron gets when under a given potential V, that is, E = e·V, being here e the elementary charge. This is how an electron gun works, Right? Asuming non-relativistic mechanics, that energy E is the classic kinetic energy, Ek = ½mv2, which is a good approximation for low voltages. But assuming relativistic mechanics, it is c·p, so c·p = e·V, and thus Et2 = E02 + e2V2. From here on, the theory follows all what you, Ldm1954, have stripped out.
 * As you left it, there is no way for the reader to know how to compute 1/k (the wavelength &lambda;, the magnitude we're interested to get) from the applied voltage V. Plus, you're using k as an input value, not the output one.
 * Conclusion: the former theory section must be re-stated at least as an introductory reasoning. Then, that "effective mass adjusted to cancel out the relativistic terms" can be addresed, if necessary, but in such way k being the resulting, deduced value. 37.134.90.176 (talk) 21:40, 17 February 2023 (UTC)
 * Thankyou for noting the typo, which is now corrected.
 * Please read the work by Fujiwara (1961), that of Howie (1962) and also other papers such as the more recent Watanabe et al (1996) cited. All electron diffraction theory start from either the Dirac equation or Schroedinger with the effective mass. They do not start with the work of De Broglie, they start with quantum mechanics. Sorry. Ldm1954 (talk) 23:49, 17 February 2023 (UTC)
 * Dirac's equation (1928) derived from Schrödinger wavefunctions (1925-1926) for (non-relativistic) both planar waves (leading to Klein–Fock–Gordon equation, 1926) and the hydrogen atom, which in turn extend De Broglie's hypothesis (&lambda; = h/p, 1924) and his hydrogen atom's model (electron as stationary wave with &lambda;n = 2&pi;na0, being n the principal quantum number, with n &#x2208; &#x2115;), which in turn explain Bohr's hypothesis (1913) of quantized states and angular momentum of the hydrogen atom (Ln = m0rnvn = nh/2&pi;), to be succint. So yes, De Broglie's work IS quantum mechanics, check the years. In fact, the starting point of quantized wave mechanics was De Broglie, not Schrödinger. This is stated in every high school physics' book since then, and elsewhere here in the Wikipedia, of course.
 * I agree De Broglie himself didn't anticipate electron diffraction (as he didn't anticipate the electron microscope, to say), but the famous Davisson–Germer experiment (1927), the first evidence of the particle-wave duality postulated by De Broglie, was by the discovery that electrons diffract for real, which it is possible only if accelerated electrons behave as De Broglie said. This is the key link.
 * After your last edit, there are now two flaws:
 * By substituting meff in the first of the two equations involving E and meff (BTW, I would prefer a subscript for meff), being here E = e·V Joules and the wavelength &lambda; = 1/k, one reach finally $$\frac{1}{k}=\lambda=\frac{hc}{\sqrt{eV(2m_0c^2+eV)}}$$ (try it by yourself), which is exactly the same conclussion in the former "theory" section, "Relativistic" sub-section, that what you say it is "wrong". It's not (or if yes, yours too).
 * You stated that E is typically given in electronvolts (eV), but the shown formulae are for energy in Joules (SI). This only gets the unaware audience more confused.
 * The main conclusion here is that, essentially, you've vandalized the whole article, as me and others complain about. Your exposition is not superior than previous, so please desist. 37.134.90.176 (talk) 02:32, 18 February 2023 (UTC)
 * Unfortunately you are still missing the key point. Let me try and explain it differently.
 * Yes, De Broglie's work was important. Nobody has ever said it was not.
 * However, it is not central to 21st century understanding of electron diffraction. The key paper is by Bethe (1928), as cited in the article and in articles/textbooks on dynamical diffraction. He starts with the non-relativistic Schroedinger equation, from which by assuming plane wave solutions he derives the basic form of the secular equations for a periodic potential and reciprocal lattice. He even has mean inner potential effects and aspects of the dispersion surface.
 * The effective mass is how the errors in the Schroedinger equation are handled for elastic scattering. (Inelastic is different.) This is the foundation of all modern methods such as multislice and channeling. The wavelength has some relevance, but is not in fact a constant inside a solid, as we know from band structure -- but this is well, well beyond what is relevant here.
 * Please read Bethe's paper. Sorry, but this matters. Ldm1954 (talk) 03:45, 18 February 2023 (UTC)
 * Addendum: I have added back the equation for the wavelength. I don't think it is useful, but Klingm01 thinks it is. It is not an important change. Ldm1954 (talk) 04:17, 18 February 2023 (UTC)
 * Still far from being satisfactory, specially for introducing the topic to a broader audience and students. It seems you only address those who already know about the subject. The article is not about 21st century understanding of electron diffraction only, you know.
 * De Broglie's key formula, $$\lambda=h/p$$ should be cited, at least, along with his original non-relativistic deduction of the wavelength for electrons accelerating under a potential V, with $$E_K=e\cdot V$$, leading to $$\lambda=\frac{h}{\sqrt{2m_0 eV}}$$, and noting this is a good approximation only for low voltages, of about 100V or so.
 * The general, relativistic formula can be summarized as follow: given in special relativity both:
 * $$E_t=m_0 c^2+E$$ and $$E_t=\sqrt{m_0^2 c^4+p^2 c^2}$$
 * for the total energy $$E_t$$ of a single electron, then
 * $$m_0 c^2+E=\sqrt{m_0^2 c^4+p^2 c^2}$$.
 * By squaring, cancelling the resulting $$m_0^2 c^4$$ at both sides and extracting $$E$$ as common factor at left side,
 * $$E(2m_0 c^2+E)=p^2 c^2$$.
 * As per De Broglie, $$\lambda=h/p$$, so $$p=h/\lambda$$. By substituting $$p^2$$ and solving for $$\lambda^2$$ we get:
 * $$\lambda^2=\frac{h^2 c^2}{E(2m_0 c^2+E)}$$. (1)
 * With $$E=e\cdot V$$, electron wavelength is
 * $$\lambda=\frac{hc}{\sqrt{eV(2m_0 c^2+eV)}}$$.
 * The original table of wavelengths by potential, which is fully correct, should be restored.
 * Notice: if $$E$$ is given in electronvolts, then one must use $$m_0 c^2\approx 0.511$$ MeV, not joules.
 * To the wavefunction: continuing from (1), lets introduce a convenient value $$k=\frac{1}{\lambda}$$, and extracting $$2c^2$$ as common factor in the divisor:
 * $$\frac{1}{k^2}=\frac{h^2}{2E(m_0+\frac{E}{2c^2})}$$.
 * Lets introduce a new convenient value $$m^*=m_0+\frac{E}{2c^2}$$, sometimes called the electron "effective mass" by some authors [refs here]. Note this value is a shorthand akin to concepts like the reduced mass for solving the two-body problem, or the Lorentz factor in special relativity, not a true physical magnitude.
 * Then, by substituting with $$m^*$$ and solving for $$E$$:
 * $$E=\frac{h^2 k^2}{2m^*}$$.
 * And etc., up to $$\psi(r)$$, showing $$k$$ is the so-called wavevector.
 * This way, the full historical path is shown step-by-step, giving the complete picture without too much overload. Then you can discuss diffraction formulae next.
 * Plus, wavelength IS relevant to understand how accelerated electrons reach the sample where diffraction occurs. If not, there would be no difference as if discussing pure X-rays diffraction here. 37.134.90.176 (talk) 02:22, 23 February 2023 (UTC)

Please check the established literature
To repeat, please read the seminal paper by Bethe (1928) in order to understand more about the foundations. This is the established explanation, and starts from the Schroedinger equation, not the De Broglie relationship. It appeared within months of the experiments. Indeed, if you look at the original experimental papers (cited in the document) you will see that they hedge between using the De Broglie approach, and what was call undulatory mechanics, what we now call quantum mechanics or wave mechanics.

Also, please read up on effective mass using, for instance, Ashcroft and Mermin and semiconductor theory. It is far from what you are suggesting, and has real physics behind it, for instance holes in solid-state physics. It is not close to reduced mass or similar. Strictly speaking it is a tensor $$h^2/m_{ij}^* = d^2E(k)/dk_idk_j$$, but we can simplify to $$h^2/m^* = d^2E(k)/dk^2$$ except in elements of dynamical theory -- but this is a big digression.

Maybe an example will help. We all know about shock waves and sound, also the sound waves in solids which are called phonons. These are collective oscillations of atoms, and can be described as both particles and waves. They have mass, which is not that of individual atoms but an effective mass as mentioned above. Almost every on has an effective mass, for instance plasmons, magnons -- see List_of_quasiparticles. Tricky physics which is beyond the scope of this article IMHO. Ldm1954 (talk) 03:12, 23 February 2023 (UTC)

Electron diffraction on crossroad
The article seems to divert from important Wikipedia standards.

Instead of addressing particular problems with the article content and structure, let me mention something more fundamental - the conflict I see between the recent direction of this article and general philosophy of Wikipedia.

This is encyclopedia
Dear Ldm1954, I do respect your expertise, but this is not a textbook, this is not your lecture, this is not your show. This is encyclopedia.

The purpose is not to generate as much content as possible, but to explain things in a generally understandable way.

The purpose is not to show off our expertise and burry the reader under an avalanche of advanced physics, but to make it understandable to broader audience with expectable amount of their effort, time and expertise.

The purpose is not to scare the readers but to attract them. Not to discourage them even from reading Wikipedia article but to show them "hey, it's not a rocket science... YOU CAN make it, YOU WILL make it" and then to encourage them to look for more... Not to build a cliff in front of them, but to offer them a staircase.

Wikipedia is not here for you, it is not here for me, it is here for the reader.

It is not about you, it is not about me, it is about the reader.

Wikipedia is a living organism
Dear Ldm1954, as mentioned above, Wikipedia is not a textbook. Printed textbooks do not change very often. Wikipedia does. And, in fact, it is one of its fundamental strengths. Please do realize, however unacceptable it might sound to you, that you are not the last author of this article. If any other author wants to add an image for instance, they will be forced to re-number all the figures and references below the added image. If any other author wants to add an image between the first and second one (as you call them Figure 1 and 2), they would need to fix the numbering at almost 60 places across the whole article. I don't know if this is your way how to intentionally cement the article in the shape you've got it into, but this is definitely not the way how the things are done here.

You're also breaking the convention of how bold text is used - it is definitely not used to emphasize "Figure 18". Personally, I do not fully agree with how bold text is (or rather isn't) used on Wikipedia either, but I do respect it. Ldm1954, please do stop with offenses and threats and start observing and listening.

The crossroad
Dear editors and readers,

It seems to me the article have reached a crossroad. However I respect Ldm1954's expertise and effort, he has overwritten the article in spite of numerous objections regarding the structure, content, sources etc. I hope this have lead the article far from Wikipedia standards and legitimate expectations of the readers. Since I can be biased, I would like to ask you for your opinion.

Please help us to find the best way - express your opinion and suggest how the article should look like:
 * 1) Take a look at the  original version of the article,  current version and perhaps the discussion above.
 * 2) Express your opinion not limited to the scientific point of view.
 * 3) If you don't find the present state ideal, then please suggest how the article should (or should not) look like, what it should (or should not) contain and potentially how the desired state should be reached.

Thank you.

Dear readers, please note you can participate in the discussion without being Wikipedia editors.

Dear Ldm1954, since we both can be biased, I am sure you will agree it is best for you (Ldm1954) and me (Klingm01) to abstain from the discussion (feel free to react to my post in Reactions, however). I would also ask you not to edit the article until this is resolved.

Klingm01 (talk) 10:10, 2 March 2023 (UTC)

For the record

 * Dear User:Klingm01,


 * I have asked you numerous times in this overlong thread to read the literature, which will clarify your questions. I have also suggested some positive additions such as Ewald sphere; since you did not respond I have already included that for TEM, LEED & RHEED.
 * I realise that you put effort into a version, but it had serious issues. Wikipedia articles have to be correct, they should not contain major errors of science. Equally important they need to be properly cited, both in terms of who did what as well as when points are made (as User:Theroadislong has mentioned).
 * I do not want to inflame this further, but at the same time it is worth detailing some of the main issues with the version as of the end of 2022:

General

 * Contains 20 cites, compared to 135 in the revised version.
 * Frequently cites the software of User:Klingm01, not that of others.
 * Focuses mainly on selected area electron diffraction. While this is useful it is only a small part.
 * Contains many, many errors in citations, for instance the book by Fultz and Howe is missing Jim Howe (there are others).

History

 * Omitted Faraday, Julius Plücker. did not correctly identify the image as a Crookes tube, Stoney.
 * Misrepresented de Broglie's work -- please read his thesis.
 * Omitted Schrödinger whose importance de Broglie recognised (see quote in current version).
 * Incorrect credit to original electron diffraction experiments, gas diffraction and who invented the electron microscope (authors missing and not properly cited).
 * Stops in 1932, and does not mention anything more.

Theory

 * Incorrectly states that electrons just interact with the positive nucleus.
 * Confuses combined elastic & inelastic, they occur simultaneously and cannot be separated (Copenhagen interpretation).
 * Omits relativistic effective mass -- critical
 * Incorrectly states that only Bragg diffraction occurs (Figure and angle).
 * Gives incorrect equation for kinematical diffraction, omitting temperature factors and depth/excitation error dependence.
 * Incomplete sources cited for Kikuchi
 * No sources for GED

Applications

 * Confused statement about Ewald sphere introduced without explanation or citation.
 * No cites to other methods.
 * No cites to electon optics.
 * Omits LEED
 * Omits RHEED
 * Omits PED
 * Omits electron crystallography (no cites) to solve structures.


 * I think it is better to move forward. At present the page is missing good experimental examples of double diffraction, superstructures, incommensurate structures and diffuse scattering. While these should not be vast, they are important and merit a paragraph. Please focus on these rather than the wavelength.


 * For refence, I suggest looking at X-ray crystallography (which is perhaps too long, as others have said) for comparison and as a guide. — Preceding unsigned comment added by Ldm1954 (talk • contribs) 13:26, 2 March 2023 (UTC)

Article opinions and suggestions (no Klingm01, no Ldm1954)
I have no opinion on the content of the article, it is mostly incomprehensible to an arts based layman like myself, however I do agree that the use of numbered figures should be removed, that is not how we use illustrations in articles. Theroadislong (talk) 13:24, 2 March 2023 (UTC)


 * The problem is that some of the Figures require cross-referencing at different locations. Removing bold is not an issue, but do you have a solution for that? Ldm1954 (talk) 13:28, 2 March 2023 (UTC)
 * Please provide a cite to your statement "the use of numbered figures should be removed, that is not how we use illustrations in articles". When I read the Wikipedia information nothing is stated. Ldm1954 (talk) 21:24, 3 March 2023 (UTC)
 * In 16 years of editing here, I've not seen this method used and it doesn't seem necessary here. Theroadislong (talk) 21:37, 3 March 2023 (UTC)
 * I have seen it in some other pages, admittedly a minority. As just one example, Figures 6, 17 and 19 are all Ewald sphere constructions of different types, relevant both to the general discussion within Geometry of diffraction and the more specific LEED and RHEED sections. This is technically correct. On non-technical issues I will defer to your expertise, but not on technical ones such as this. Ldm1954 (talk) 21:43, 3 March 2023 (UTC)
 * Ok, it's a mess but if you think it is required, I will not argue further, it will be a nightmare for anyone adding further images in future. Theroadislong (talk) 21:54, 3 March 2023 (UTC)

Topic expert
User:Ldm1954 you may be a topic expert, BUT we still require references for any content that you add. Theroadislong (talk) 17:29, 13 May 2023 (UTC)


 * They are already there. Ldm1954 (talk) 17:35, 13 May 2023 (UTC)
 * You may consider it "pedantic", and tiresome, but it is absolutely required that all content is correctly sourced. Theroadislong (talk) 20:36, 13 May 2023 (UTC)

Equations and vectors
Proper vector notation should be used when needed, I cannot tell which $$r$$ should be $$\mathbf r$$ and which $$r.k$$ should be replaced by $$\mathbf r \cdot \mathbf k$$. ReyHahn (talk) 14:09, 27 April 2023 (UTC)


 * A good suggestion, done. Ldm1954 (talk) 20:14, 27 April 2023 (UTC)

Topic expert
User:Ldm1954 you may be a topic expert, BUT we still require references for any content that you add. Theroadislong (talk) 17:29, 13 May 2023 (UTC)


 * They are already there. Ldm1954 (talk) 17:35, 13 May 2023 (UTC)
 * You may consider it "pedantic", and tiresome, but it is absolutely required that all content is correctly sourced. Theroadislong (talk) 20:36, 13 May 2023 (UTC)
 * As you have yourself stated before, science is not your area. Therefore it is understandable that you do not realise that terms & content have already been sourced, often within a sentence. Your statements about lack of content sourcing are highly inappropriate. For instance, the book by Born and Wolf has extensive information on classic wave, aperture, Fresnel and Fraunhofer diffraction. Please stop making such comments, they are not constructive. Ldm1954 (talk) 20:50, 13 May 2023 (UTC)
 * Science is not my area but Wikipedia is, and correct sourcing is imperative per 5P2 which states that "all articles must strive for verifiable accuracy, citing reliable, authoritative sources." Theroadislong (talk) 20:59, 13 May 2023 (UTC)
 * To repeat, it was always there. Ldm1954 (talk) 21:05, 13 May 2023 (UTC)
 * @Theroadislong Is there some specific concerns you have? To me, this is a comprehensive article with a very large number of references and cross links. Johnjbarton (talk) 17:40, 16 May 2023 (UTC)
 * I was concerned that the editor was adding content and comments based on their knowledge of the topic rather than referencing the sources. Happy to be shown the error of my ways. Theroadislong (talk) 08:12, 18 May 2023 (UTC)

History Section revised
The 2022 History section had a number of major issues. Parts of it appear to have been copied verbatim from other Wikipedia pages, some major contributions were not mentioned, many of the links were inaccurate or broken.

The current version is based upon searching various sources which are quoted in the article. Whereas the 2022 version had 11 cites, the current one has 63. The current version:
 * Has a more general description of electrons in vacuum, with more accurate citations.
 * Puts the work of de Broglie and Schroedinger better into context, including a quote on this from de Broglie.
 * Provides credit to at least some of the founders of electron optics.
 * Provides more extensive cites to the issues about who invented the TEM, which is not straightforward. I have attempted to be unbiased.
 * Added the critical paper by Boersch on SAED.
 * Added a bit about LEED/RHEED
 * Added something about how ED was viewed for many years using a quote from John Cowley,
 * Added a bit about advances. I do not think this is the place for more.

N.B., There might be duplicate references. Ldm1954 (talk) 20:53, 18 February 2023 (UTC)
 * Just a note, the tidbit which in turn is connected to the observations of electrostatic charging by Thales of Miletus around 585 BCE. references this paper which says in its abstract "there is no basis to believe [Thales] discovered, carried out experiments on, or systematically observed electrostatic charging." I haven't read the paper; it just caught my attention as I was skimming the History section. Wanted to make sure it's as intended. Ajpolino (talk) 05:02, 28 February 2023 (UTC)


 * Ajpolino it's a tricky point, and I deliberately used the word connected rather than discovered. As Daniel Lacks indicates, there is no proof -- but then our records are incomplete. For certain Thales knew of Triboelectricity charging, and the source of electron is the Greek word for amber. There is a Greek stamp with him, charging and amber, and many cites with stronger connections.


 * Please feel free to wordsmith this is sentence, it is generally accepted color rather than being critical. Ldm1954 (talk) 09:51, 28 February 2023 (UTC)

Schrödinger's removal and other suggestions
Firstly, most moderm physics prefer to use $$\hbar$$ instead of the original Planck h. Is this not the case in electron diffraction? Also modern books use $$2\pi/\lambda=k$$ and not $$1/\lambda=k$$ again is this special convention?

Secondly I suggest that the picture of Schrödinger has to go, the article has too many pictures and that figure is not adding to anything, he is not even the most famous physicist related to this topic (Thompson would be better but still unnecessary). Also the Schrodinger photo is not even referenced like the rest. To not rewrite the figures names every time one figure is removed or moved down, we should use a reference template, see an example here: []. ReyHahn (talk) 22:32, 27 April 2023 (UTC)


 * To clarify:
 * Please see notes c & d: the text uses the crystallography convention, which is standard in electron diffraction, not the physics convention. Using the physics notation is inappropriate, sorry. (Real & reciprocal lattice conventions similarly differ, also in the note.)
 * With the crystallography convention it is $$h$$, not $$\hbar$$.
 * Thompson has no relevance to electron diffraction, similarly Einstein, Hertz...
 * All ED theory starts with the Schroedinger equation, using Bethe's approach, it is the foundation. The quote from de Broglie's thesis is meant to indicate this (without shouting), and note b points out that Davisson and Germer knew, please check the ref if needed (I did). The text also tries to indicates this without shouting. (The methods use either Bloch waves, a Green's function approach or tight-binding, similar to band structure, but this is a massive digression.)
 * While automatic numbering of Figures would be nice, that template would not make it easy to cross-reference images. In the text there is need to specifically refer to these for the different cases at different places in the text. For instance, the Ewald sphere results are very different for TED, RHEED & LEED. This needs to be mentioned in the geometry, but the Figures themselves belong with the relevant text.
 * Finally, electron diffraction (and imaging) is image oriented. An image to illustrate each and the relevant Ewald sphere is consistent with standard useage. I see no harm in the images.
 * Discussion is good, particularly input from outside the field. Ldm1954 (talk) 02:59, 28 April 2023 (UTC)
 * Thanks you for clarifying the convention with respect to hbar, it makes sense now. Regarding the template, I think it allows to call a figure several times. As for the figures themselves, I see no harm on having an illustrated article, I just would prefer it to not be over illustrated a photo of Schrödinger is not clarifying anything.--ReyHahn (talk) 12:18, 28 April 2023 (UTC)
 * OK. If you were unsure, then I need to explain the notation issue better. I suspect that just having a note is not enough, it needs to be more "see Note xyz" or similar. Some wordsmithing needed.
 * I will play with that template in my Sandbox "soon", to see if I can tweak it into something comparable to standard publication labelling. I will do that before reconsidering the image, which is admittedly not so critical. Ldm1954 (talk) 12:26, 28 April 2023 (UTC)
 * N.B., you don't like Brownies? A touch of humor is needed, let's not fall asleep with dryness. Ldm1954 (talk) 19:55, 28 April 2023 (UTC)
 * See WP:JOKE.--ReyHahn (talk) 12:08, 3 May 2023 (UTC)

Proposed less steep intro text for Electron Diffraction
Please see User:Johnjbarton/Electron_Diffraction_Sandbox

This version drops the intro text "Close to the atoms the changes are described as Fresnel diffraction; far away they are called Fraunhofer diffraction. " IMO here is too early and it's covered later. Also drops the note as the intro covers naturally now.

Overall I was going for a positioning with linking that set expectations.

Please feel free to use, edit, or ignore as you like. Johnjbarton (talk) 01:27, 17 May 2023 (UTC)


 * I like the concept, and will use it with (perhaps) a few changes. Within a few days, I have some paperwork to do first. Ldm1954 (talk) 11:48, 18 May 2023 (UTC)
 * I just tried, and failed. The problem is that "electron diffraction" is a generic term in normal usage for both diffraction patterns and dynamical scattering. In 99.99% of cases there are not "obstacles", they electrons change direction due to quantum mechanical elastic scattering. Therefore the idea that there is interference between different paths is not really correct for the general sense, only for diffraction patterns. I cannot find a way to incorporate these changes without making statements that are not right or might be inappropriate. Sorry. Ldm1954 (talk) 15:59, 6 June 2023 (UTC)
 * Re-reading I agree. I reworked it. Please take another look. In any case I think re-working the Electron Diffraction intro is worth effort. Johnjbarton (talk) 17:02, 6 June 2023 (UTC)
 * OK. I will have a other go in a day or so. Ldm1954 (talk) 17:04, 6 June 2023 (UTC)

Adding an image of quasicrystals might be more informative?


We could use an image of the diffraction of a quasicrystal in the "Aperiodic materials" sub-sub-section. This would really show the "aperiodicity" of the diffraction patterns of such materials. Currently, I am looking at figure 15 and I cannot understand why it is aperiodic from the first glance. However, the diffraction patter of a quasicrystal is obviously aperiodic. TheLonelyPather (talk) 00:04, 17 August 2023 (UTC)


 * i am OK with replacing the current Figure 15 -- it's not mine, but she won't mind. The text would need to be changed with a high-schools explanation of how it is aperiodic in a few sentences. Do you want to take a stab at it in the talk? Ldm1954 (talk) 01:36, 17 August 2023 (UTC)
 * All right, I will give it a try...
 * An extreme example of aperiodic materials is for quasicrystals. Atoms in quasicrystals are ordered, but they do not have a repeating pattern and has no translational symmetry. An example is given in Figure 15...
 * I am not very sure how to introduce the image through the text, and I don't know enough sources to properly introduce quasicrystals. please go for it. I trust in your expertise. TheLonelyPather (talk) 13:07, 17 August 2023 (UTC)
 * Thanks for the description. I could not find a description for the particular DP that is shown, so I have used one of mine which is decent, but perhaps not so good. If you can find a description (and reference) for the one on the aperiodic page I will switch. Ldm1954 (talk) 19:18, 17 August 2023 (UTC)

Names
Can we write the full names of scientists when first named in the article? If this was a scientific journal there will be no problem but as this is a large encyclopedia many authors with the same last name exist. Also it allows for quicker recognition (and it does not affect word count that much). ReyHahn (talk) 00:54, 10 October 2023 (UTC)


 * Done, although I could not find a few. I am going to post a related question on links to the Physics page. Ldm1954 (talk) 14:39, 11 October 2023 (UTC)

Lead sentence.
A suggestion for the first sentence:

Electron diffraction refers to the change in the direction of electron beams passing near atoms and the use of that phenomenon to study materials at an atomic level.

IMO the first sentence should not have a footnote. Details belong in the article. Johnjbarton (talk) 02:28, 11 November 2023 (UTC)

Image captions
regarding your figures that have multiple images, could you rework the captions to be less layout dependent? For example, Figure 2 says "The first is the Young's slit experiment..." Depending on how the article is being presented, it may not be clear which one is the first. Likewise with Figures 9, 10, 13 referring to left and right. And Figure 3 (3A?) with top and bottom. This is all related to MOS:ACCIM. RoySmith (talk) 17:50, 17 September 2023 (UTC)


 * I have edited the captions so if they somehow get reordered which one is referred to should be clear. For instance instead of "The first..." in Figure 2 I have removed "The first" and mentioned the color of the wave and slits.
 * N.B., since they are composite images, at least on my computer, android phone and tablet they remain grouped together -- they are just shrunk. Ldm1954 (talk) 18:31, 17 September 2023 (UTC)