Variational determination of ground and excited-state two-electron reduced density matrices in the doubly occupied configuration space: A dispersion operator approach

ALCOBA, DIEGO R.; OÑA, OFELIA B.; LAIN, LUIS; TORRE, ALICIA; CAPUZZI, PABLO; MASSACCESI, GUSTAVO E.; RÍOS, ELÍAS; RUBIO-GARCÍA, ALVARO; DUKELSKY, JORGE

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Año: 2021 vol. 154

0021-9606

This work implements a variational determination of the elements of two-electron reduced density matrices corresponding to the ground and excited states of N-electron interacting systems based on the dispersion operator technique. The procedure extends the previously reported proposal [Nakata et al., J. Chem. Phys. 125, 244109 (2006)] to two-particle interaction Hamiltonians and N-representability conditions for the two-, three-, and four-particle reduced density matrices in the doubly occupied configuration interaction space. The treatment has been applied to describe electronic spectra using two benchmark exactly solvable pairing models: reduced Bardeen-Cooper-Schrieffer and Richardson-Gaudin-Kitaev Hamiltonians. The dispersion operator combined with N-representability conditions up to the four-particle reduced density matrices provides excellent results.