Dear Wien2k users and developers, I'd like to refresh the discussion about the total energies of the charged cells which took place three years ago: http://zeus.theochem.tuwien.ac.at/pipermail/wien/2007-January/008711.html
I'm trying to calculate the formation energy of the Hydrogen vacancy in +/-1 charge states and find that the results are bad (much differ from the literature) although the formation energy of the neutral hydrogen vacancy is good. So my question arises if we can trust the values of the total energies for the charged cells in the recent version of Wien2k? To investigate this issue further I have performed the following tests: I've done the calculations of the total energy of Mg, MgH2 and GaN for three cases: neutral cell, cell with one electron removed (+1 charge) and a cell with an electron added (-1 charge). The results were compared with the same calculation with another plane-wave code and are the following: ----------------------------------------- hcp Mg: Wien2k: E(+1)-E(0) = 0.245 Ry E(-1)-E(0) = -0.199 Ry Plane-Wave code: E(+1)-E(0) = -0.226 Ry E(-1)-E(0) = 0.281 Ry bcc MgH2 Wien2k: E(+1)-E(0) = 0.277 Ry E(-1)-E(0) = 0.085 Ry Plane-Wave code: E(+1)-E(0) = 0.024 Ry E(-1)-E(0) = 0.326 Ry fcc GaN Wien2k: E(+1)-E(0) = 1.12 Ry E(-1)-E(0) = -0.717 Ry Plane-Wave code: E(+1)-E(0) = -0.151 Ry E(-1)-E(0) = 0.443 Ry ------------------------------------------------- In wien2k the charged cell was created by changing the number of electrons in case.in2 and adding the corresponding background charge in case.inm. One can observe, that the energies have the same order of magnitude, but the sequence of energies E(+1), E(0) and E(1) is inverse. It seems, that the system with +1 charge (electron removed) behaves like the system with -1 charge in the Plane-Wave code. Of course, the results of tests are not physical, because no supercell was used and no geometric relaxation was performed (however, it is not needed for Mg), but if one tries to do all the supercell and relaxation stuff and tries to calculate the defect formation energy, the result will be the same. I'd be grateful if you comment on this and suggest any corrections which should be provided to the total energies for the charged cells. with kind regards, Yurko -- 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