TY  - JOUR
AU  - Theophilou, Iris
AU  - Lathiotakis, Nektarios N.
AU  - Helbig, Nicole
TI  - Conditions for Describing Triplet States in Reduced Density Matrix Functional Theory
JO  - Journal of chemical theory and computation
VL  - 12
IS  - 6
SN  - 1549-9626
CY  - Washington, DC
PB  - American Chemical Society (ACS)
M1  - FZJ-2016-03134
SP  - 2668 - 2678
PY  - 2016
AB  - We consider necessary conditions for the one-body reduced density matrix (1RDM) to correspond to a triplet wave function of a two-electron system. The conditions concern the occupation numbers and are different for the high spin projections, Sz = ±1, and the Sz = 0 projection. Hence, they can be used to test if an approximate 1RDM functional yields the same energies for both projections. We employ these conditions in reduced density matrix functional theory calculations for the triplet excitations of two-electron systems. In addition, we propose that these conditions can be used in the calculation of triplet states of systems with more than two electrons by restricting the active space. We assess this procedure in calculations for a few atomic and molecular systems. We show that the quality of the optimal 1RDMs improves by applying the conditions in all the cases we studied.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000378016000016
C6  - pmid:27171683
DO  - DOI:10.1021/acs.jctc.6b00257
UR  - https://juser.fz-juelich.de/record/810279
ER  -