We extend our recently developed heat-bath configuration interaction (HCI) algorithm, and
our semistochastic algorithm for performing multireference perturbation theory, to calculate …

Selected configuration interaction (sCI) methods including second-order perturbative
corrections provide near full CI (FCI) quality energies with only a small fraction of the …

A hybrid stochastic-deterministic approach for computing the second-order perturbative
contribution E (2) within multireference perturbation theory (MRPT) is presented. The idea at …

The concept of Dyall zeroth-order Hamiltonian [Dyall, KGJ Chem. Phys., 102, 4909-4918
(1995)] has been instrumental in the development of intruder-and parameter-free …

The electronically excited states of methylene (CH2), ethylene (C2H4), butadiene (C4H6),
hexatriene (C6H8), and ozone (O3) have long proven challenging due to their complex …

We introduce a new variant of the complete active space second-order perturbation theory
(CASPT2) method that performs similarly to multistate CASPT2 (MS-CASPT2) in regions of …

We reexamine ΔCCSD, a state-specific coupled-cluster (CC) with single and double
excitations (CCSD) approach that targets excited states through the utilization of non-Aufbau …

Light–matter interaction is crucial to life itself and revolves around many of the central
processes in biology. The need for understanding these photochemical and photophysical …

Over the last decade, the second-order N-electron valence state perturbation theory
(NEVPT2) has developed into a widely used multireference perturbation method. To apply …

The implementation of multireference configuration interaction (MRCI) methods in quantum
systems with large active spaces is hindered by the expansion of configuration bases or the …