Dear Users, in my investigations on the electronic structure of bulk MoS2 I encountered a surprising outcome from my Lowdin charge analysis. Using for Mo an ultrasoft PBE pseudo with semi-core state in valence (I think I have correctly converged all the calculation parameters) I get the odd result that the metal atom is slightly negatively charged (about 0.46 e-) w.r.t. the sulfur centre (which is about 0.29 +). The p orbitals of the Mo atom are filled by 7 electrons, which is odd as well. A similar reversed behaviour is shown by considering a single S atom on a 3-layered iron slab.
While I do not expect the absolute numbers to be too accurate, I am nevertheless confused by the reversed, counterintuitive polarity. I also noted that if I just take into account the outer valence orbitals (that is, 4d for Mo and 3p for S) the situation gets slightly better, as in this case the S atom shows a 0.12 e- accumulation on the 3p. Do you think that for covalent compounds such as MoS2 a reliable Lowdin analysis is rather unfeasible or - as I think - I am missing some point in evaluating its outcome? When I consider charge transfers, should I focus on the outer valence states and leave the total charge? Thanks a lot for any comment. Have a nice WE! Giacomo Levita (post-doc, CNR-Nano, S3 Modena, Italy)
