User:Dec40upitt/sandbox

History of CHelpGpbc
The CHelpG (CHarges from Electrostatic Potentials using a Grid based method) was developed by Breneman and Wiberg, where atomic charges are fitted to reproduce electrostatic potential at various grid points around a molecule. This CHelpG method has been revised and extended to systems with periodic boundary conditions, i.e., CHelpGpbc.

Codes
The tutorial of using the code for computing atomic charges for periodic systems, such as metal-organic framework, is provided. The details of charge fitting algorithm and effects of several important parameters was discussed by Chen et al. (J. Karl Johnson group, University of Pittsburgh) A similar algorithm was reported by Campañá et al.

How to get a copy of this code? Link is available for downloading.

How to use this code? The document will come out soon...

Features:
 * Point selection.




 * Comparison of Ewald and Wolf summation.

Files
Three files are necessary to run the code: INPUTFILE, SYMMINP, and LOCPOT.
 * INPUTFILE: Keywords specify values for various parameters.
 * inner_vdw_fac
 * outer_vdw_fac
 * element
 * kmax
 * alpha
 * grid_thin
 * constrain
 * lrc_method
 * restrain
 * symmetry
 * esp_output
 * pdb_output
 * xyz_output
 * normalization


 * SYMMINP file: Symmetry of the system is given.
 * LOCPOT file: Electrostatic potential from quantum chemical calculations (Vienna Ab-initio Simulation Package (VASP)).