Ground and Excited State First-Order Properties in Many-Body Expanded Full Configuration Interaction Theory

TL;DR

This paper extends the many-body expanded full configuration interaction (MBE-FCI) method to excited states and first-order properties, enabling efficient calculations of excitation energies and dipole moments without wave function sampling.

Contribution

The authors develop and demonstrate an extension of MBE-FCI to compute excited states and static properties, reducing memory requirements and broadening application scope.

Findings

Accurate excitation energies for LiH and MgO.

Reliable dipole moment calculations without wave function sampling.

Memory overhead scales with property dimension.

Abstract

The recently proposed many-body expanded full configuration interaction (MBE-FCI) method is extended to excited states and static first-order properties different from total, ground state correlation energies. Results are presented for excitation energies and (transition) dipole moments of two prototypical, heteronuclear diatomics---LiH and MgO---in augmented correlation consistent basis sets of up to quadruple-$\zeta$ quality. Given that MBE-FCI properties are evaluated without recourse to a sampled wave function and the storage of corresponding reduced density matrices, the memory overhead associated with the calculation of general first-order properties only scales with the dimension of the desired property. In combination with the demonstrated performance, the present developments are bound to admit a wide range of future applications by means of many-body expanded treatments of electron correlation.