Abstract

The nucleus-electron coupled self-consistent field (NECSCF)1 is extended to reduced density matrix functional theory (RDMFT) to allow computation of the nucleus-electron correlation in the presence of electron-electron correlation in many-electron system. The nucleus-electron and electron-electron correlation potentials are reformulated by the cumulant expansion of the conditional reduced density matrix. An entropic RDMFT functional2 is applied to evaluate the exact potential, which builds the connection between the orbital energies and the Fermi-Dirac distribution of occupation numbers. The nucleus-electron correlation is recovered accurately with a similar computational cost with the mean-field computation through a new self-consistent minimization procedure with the Fermi-Dirac distribution. The approach demonstrates the nonadiabatic effect on the occupation numbers and the molecular bonding character in the correlated many-electron system over a single potential energy surface against the uncorrelated mean-field NECSCF.

Reference:

1. Chen, Z.; Yang, J., J. Chem. Phys., 2021, 155, 104111-104119
2. Wang, J.; Baerends, E. J., Phys. Rev. Lett., 2016, 128, 013001-013006