Dear DFT+U experts,I am wondering how to know what is the ground state of a DFT+U calculation from an ab initio point of view. As approximated DFT is not variational I think I cannot use the total energy as an argument.
In my case I have calculated the electronic structure of NdCo in the CsCl structure type using QE-6.6. The f-orbitals splits into three representations: au, t2u and t2g. For Nd, I expect that it has a valency of three and that the t2g orbitals are fully occupied for one spin. However, I find that occupying the three t2g orbitals by 2/3 and the au orbital by one electron yields a lower energy than the expected occupation. So I wonder if I can trust in this "ground state" that is against my intuition or if this is a well known effect of DFT+U.
All hints are welcome, best regards, Malte -- Malte Sachs Anorganische Chemie, Fluorchemie Philipps-Universität Marburg Hans-Meerwein-Straße 4 35032 Marburg (Paketpost: 35043 Marburg) Tel.: +49 (0)6421 28 - 25 68 0 http://www.uni-marburg.de/fb15/ag-kraus/
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