## apbs-users

 [Apbs-users] Energy errors in APBS From: Bob Johnson - 2006-03-18 00:00:16 ```Hello everyone, I seem to be getting large discrepancies when calculating the electrostatic energy due to two charges. My system consists of two charges of +e separated by 3 angstroms. The energy calculated analytically and with the APBS coulomb program gives 463 kJ/mol. However, when I run APBS and solve the PBE with a gridsize of 129, pdie = 1, sdie = 1, I get a total electrostatic energy that is 10 times too large. Does anyone have any idea what could be going wrong? Thanks, Bob Johnson ```
 Re: [Apbs-users] Energy errors in APBS From: Nathan Baker - 2006-03-18 00:03:11 ```Hello -- PB solvers don't do terribly well at reproducing Coulomb's law at short distances (that's why the PB solver is typically used to calculation *solvation* contributions to energies and forces). What sort of grid spacings and boundary conditions are you using? Also, have you looked at the examples/coulomb test cases? Thanks, Nathan On 3/17/06, Bob Johnson wrote: > Hello everyone, > I seem to be getting large discrepancies when calculating the electrostat= ic > energy due to two charges. My system consists of two charges of +e separa= ted by > 3 angstroms. The energy calculated analytically and with the APBS coulomb > program gives 463 kJ/mol. However, when I run APBS and solve the PBE with= a > gridsize of 129, pdie =3D 1, sdie =3D 1, I get a total electrostatic ener= gy that is > 10 times too large. Does anyone have any idea what could be going wrong? > Thanks, > Bob Johnson > > > ------------------------------------------------------- > This SF.Net email is sponsored by xPML, a groundbreaking scripting langua= ge > that extends applications into web and mobile media. Attend the live webc= ast > and join the prime developer group breaking into this new coding territor= y! > http://sel.as-us.falkag.net/sel?cmd=3Dlnk&kid=3D110944&bid=3D241720&dat= =3D121642 > _______________________________________________ > apbs-users mailing list > apbs-users@... > https://lists.sourceforge.net/lists/listinfo/apbs-users > > -- Assistant Professor, Dept. of Biochemistry and Molecular Biophysics Center for Computational Biology, Washington University in St. Louis Web: http://cholla.wustl.edu/ ```