DFT+U: different oxidation states on the same element (charge ordering)|
- Date: 2015/02/17 01:29
- Name: Mauro Sgroi
- Dear all,
I'm trying to simulate structures in which the same element (e.g. Fe) is in different chemical environments (e.g. different symmetry). For example I'm trying to simulate the cell of LiFePO4 (28 atoms). Removing one of the four lithium atoms I would expect that the Fe atom near the vacancy has a different charge than the remaining Fe. This is evident in LiFexMn1-xPO4, characterized by two delithiation potentials associated to the redox reactions Mn2+ -> Mn3+ + e- and Fe2+-> Fe3+ + e-.
DFT would tend to distribute the charge equally on the transition atoms, not taking into account the differences due to the Li vacancies (Science 321, 792 (2008), Aron J. Cohen et al.).
Is it possible to force the occupations through a penalty function not using non-collinear DFT?
Thanks a lot and best regards,