[Wien] Bad formation energies for the charged vacancies

[Yurko Natanzon]

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 Niewodniczański 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