Heat-bath Configuration Interaction: An efficient selected CI algorithm inspired by heat-bath sampling

TL;DR

The paper introduces Heat-bath Configuration Interaction (HCI), a new efficient selected CI algorithm inspired by heat-bath sampling, which accurately captures static and dynamic correlation in large quantum systems.

Contribution

HCI is a novel deterministic selected CI method that balances speed and accuracy using two parameters, enabling efficient treatment of large multireference systems.

Findings

Accurately computes potential energy curves for complex molecules.

Recovers full CI energies for large systems within minutes on a single core.

Handles extremely large variational spaces with high precision.

Abstract

We introduce a new selected configuration interaction plus perturbation theory algorithm that is based on a deterministic analog of our recent efficient heat-bath sampling algorithm. This Heat-bath Configuration Interaction (HCI) algorithm makes use of two parameters that control the tradeoff between speed and accuracy, one which controls the selection of determinants to add to a variational wavefunction, and one which controls the the selection of determinants used to compute the perturbative correction to the variational energy. We show that HCI provides an accurate treatment of both static and dynamic correlation by computing the potential energy curve of the multireference carbon dimer in the cc-pVDZ basis. We then demonstrate the speed and accuracy of HCI by recovering the full configuration interaction energy of both the carbon dimer in the cc-pVTZ basis and the strongly-correlated chromium dimer in the Ahlrichs VDZ basis, correlating all electrons, to an accuracy of better than 1 mHa, in just a few minutes on a single core. These systems have full variational spaces of 3x10^14 and 2x10^22 determinants respectively.