Mayer István, Pápai Imre, Bakó Imre, Nagy Ágnes
Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences , Budapest H-1117, Hungary.
Department of Theoretical Physics, Debrecen University , Debrecen H-4010, Hungary.
J Chem Theory Comput. 2017 Sep 12;13(9):3961-3963. doi: 10.1021/acs.jctc.7b00562. Epub 2017 Aug 25.
It is discussed that finite basis Density Functional Theory (DFT) calculations using a single Kohn-Sham determinant cannot reproduce, in a strict mathematical sense, the exact electron density corresponding to the same finite basis. This is because the DFT density derives from an idempotent first order density matrix, while the exact (full CI) density can only be obtained from a nonidempotent one. The problem is absent for the original Kohn-Sham integro-differential equations or if a strictly complete basis set is assumed.
有人讨论过，使用单个Kohn-Sham行列式的有限基密度泛函理论（DFT）计算在严格的数学意义上无法重现与相同有限基相对应的精确电子密度。这是因为DFT密度源自幂等的一阶密度矩阵，而精确的（完全CI）密度只能从非幂等的密度矩阵获得。对于原始的Kohn-Sham积分-微分方程或假设使用严格完备基组的情况，该问题不存在。
