I would expect there to be slight differences in the energy versus cell for the two approaches, which could easily lead to forces.
That said, I doubt that the forces will have any effect on what you are trying to calculate. Do a simple test such as a small TiO2 supercell and displace an O. --- Professor Laurence Marks Department of Materials Science and Engineering Northwestern University http://www.numis.northwestern.edu Corrosion in 4D http://MURI4D.numis.northwestern.edu Co-Editor, Acta Cryst A "Research is to see what everybody else has seen, and to think what nobody else has thought" Albert Szent-Gyorgi On Jan 29, 2016 10:04, "pavel.ondra...@email.cz" <pavel.ondra...@email.cz> wrote: > > ---------- Původní zpráva ---------- > Od: Laurence Marks <laurence.ma...@gmail.com> > Komu: A Mailing list for WIEN2k users <email@example.com> > Datum: 29. 1. 2016 13:34:23 > Předmět: Re: [Wien] force difference between LAPW and PAW method > > Did you check the absolute cell size for the two - minimize the energy > w.r.t. size? > > > The absolute cell size was fixed (same in both softwares of course) and > was calculated using experimental densities for the mixtures. No > minimization with respect to cell volume was done, however I would expect > it to be near equilibrium. My main goal with those cells is to calculate > the XPS shifts of O1s peak (using the slater transition state method) to > help in evaluation of some experimental XPS data, so I wanted to stick with > the experimental densities. > > > Would some stress in the cell explain the difference between the methods? >
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