Forcing broken symmetry to recover static electronic correlation: the H₂ molecule test case

ABSTRACT

A self-consistent field method based on a density matrix functional theory scheme is presented to compute the potential energy curve of the hydrogen molecule. A functional to recover the so-called cumulant correlation energy is introduced. The form of such functional is very simple being dependent explicitly only on the square of the overlap matrix element between the unrestricted non-orthogonal occupied orbitals of the calculation. The functional is a sum of two contributions referring to non-dynamic and dynamic correlation. The agreement with the full-CI potential energy curve is within chemical accuracy.

KEYWORDS:

• Inhomogeneous electron liquids
• electron correlation
• density matrix functional theory
• hydrogen molecule

Acknowledgments

The author wishes to acknowledge partial financial support from the University of Pisa through the project ‘Optimizing intermolecular interactions for recognition catalysis and green chemistry’ (PRA 2022 N. 34).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Università di Pisa [PRA 2022 N. 34].