Dear Prof. Blaha and Prof. Marks, Thank you for your replies. I'm afraid about the following thing: the Markove-Payne-like (Phys. Rev. B 51, 4014) correction you propose should cancel the error which exists due to the repulsion of charged defects in the periodic crystal and results in some constant energy shift. However, the problem is that the values of formation energy are not just shifted to some constant, but have the OPPOSITE signs:
If we add the correction for e.g. Mg, it will be 0.245-V_0/2 for +1 charge and -0.199+V_0/2 for the -1 charge In the Plane-Wave code which I used for comparison, the Payne-Markov corrections to the total energy is NOT applied and the values are: -0.226 Ry for +1 charge and 0.281 for -1 charge Then, it is unlikely that the addition or substracting V_0 will change the signs of both formation energies (unless V_0 also changes its sign for +1 and -1 charge states). Could it be that the problem lies somewhere else? with best regards, Yurko On 25 February 2010 17:19, Laurence Marks <L-marks at northwestern.edu> wrote: > I think the forces are going to be OK, the issue is a constant energy > correction for the nominal background charge. Since this should be > constant, I don't think it will contribute at all to forces which > depend upon gradients. -- Yurko (aka Yuriy, Iurii, Jurij etc) Natanzon PhD student Department for Structural Research (NZ31) Henryk Niewodnicza?ski Institute of Nuclear Physics Polish Academy of Sciences ul. Radzikowskiego 152, 31-342 Krakow, Poland E-mail: Yurii.Natanzon at ifj.edu.pl, yurko.natanzon at gmail.com
