I think 0.001 eV is a small quantity, and it may come from different library when you run 1 core (serial) and 12 core (parallel).
On Sat, Mar 24, 2012 at 5:50 AM, Guangping Zhang <[email protected]> wrote: > ** > ** > Dear siesta users: > > I have now encounter a question: the results differ when using different > number of core to parallel. > > 1 core: > siesta: 124 -33928.6003 -33928.6031 -33928.6366 0.0002 -4.1261 > siesta: 125 -33928.6004 -33928.6012 -33928.6346 0.0001 -4.1251 > siesta: 126 -33928.6003 -33928.6009 -33928.6344 0.0001 -4.1258 > > siesta: E_KS(eV) = -33928.6012 > > siesta: E_KS - E_eggbox = -33928.6012 > > 12 core: > > siesta: 123 -33928.6004 -33928.6064 -33928.6398 0.0003 -4.1246 > siesta: 124 -33928.6003 -33928.6026 -33928.6360 0.0001 -4.1257 > siesta: 125 -33928.6003 -33928.6018 -33928.6352 0.0001 -4.1256 > siesta: 126 -33928.6004 -33928.5996 -33928.6331 0.0001 -4.1253 > > siesta: E_KS(eV) = -33928.6001 > > siesta: E_KS - E_eggbox = -33928.6001 > > The E_KS differs 0.001 eV. I think it is significant. I think the number > of core using to paralle only affect the speed. The results should be the > same. Or there is something I am missing? > > And I have another question: when I do the geometry optimization, which > energy is used to calculated the force? And when I do molecular dynamics, > which energy is used for the force? > > I think the KS energy of a single point DFT calculation and the KS energy > of a molecular dynamics should be the same for the same structure. Am I > right? > > Any suggestions will be regarded. > > Best > > Guangping > > 2012-03-24 > ------------------------------ > Guangping Zhang > ** > -- Regards Huan Tran Department of Physics University of Basel, Switzerland Email: [email protected]
