SOiCI and iCISO: Combining iterative configuration interaction with spin-orbit coupling in two ways

Abstract

The near-exact iCIPT2 approach for strongly correlated systems of electrons, which stems from the combination of iterative configuration interaction (iCI, an exact solver of full CI) with configuration selection for static correlation and second-order perturbation theory (PT2) for dynamic correlation, is extended to the relativistic domain. In the spirit of spin separation, relativistic effects are treated in two steps: scalar relativity is treated by the infinite-order, spin-free part of the exact two-component (X2C) relativistic Hamiltonian, whereas spin-orbit coupling (SOC) is treated by the first-order, Douglas-Kroll-Hess-like SOC operator derived from the same X2C Hamiltonian. Two possible combinations of iCIPT2 with SOC are considered, i.e., SOiCI and iCISO. The former treats SOC and electron correlation on an equal footing, whereas the latter treats SOC in the spirit of state interaction, by constructing and diagonalizing an effective spin-orbit Hamiltonian matrix in a small number of correlated scalar states. Both double group and time reversal symmetries are incorporated to simplify the computation. Pilot applications reveal that SOiCI is very accurate for the spin-orbit splitting (SOS) of heavy atoms, whereas the computationally very cheap iCISO can safely be applied to the SOS of light atoms and even of systems containing heavy atoms when SOC is largely quenched by ligand fields.

References in corpus (26)

• Heat-bath Configuration Interaction: An efficient selected CI algorithm inspired by heat-bath sampling
• Semistochastic Heat-bath Configuration Interaction method: selected configuration interaction with semistochastic perturbation theory
• A deterministic alternative to the full configuration interaction quantum Monte Carlo method
• An adaptive configuration interaction approach for strongly correlated electrons with tunable accuracy
• Modern Approaches to Exact Diagonalization and Selected Configuration Interaction with the Adaptive Sampling CI Method
• The Ground State Electronic Energy of Benzene
• Excited states using semistochastic heat-bath configuration interaction
• Hybrid stochastic-deterministic calculation of the second-order perturbative contribution of multireference perturbation theory
• Excited States of Methylene, Polyenes, and Ozone from Heat-Bath Configuration Interaction
• Selected configuration interaction dressed by perturbation
• Adaptive multiconfigurational wave functions
• Equation-of-Motion Coupled-Cluster Theory based on the 4-component Dirac-Coulomb(-Gaunt) Hamiltonian. Energies for single electron detachment, attachment and electronically excited states
• Four-Component Density Matrix Renormalization Group
• Perspective: Essentials of Relativistic Quantum Chemistry
• Excitation energies from diffusion Monte Carlo using selected Configuration Interaction nodes
• One-step treatment of spin-orbit coupling and electron correlation in large active spaces
• Almost exact energies for the Gaussian-2 set with the semistochastic heat-bath configuration interaction method
• Relativistic Internally Contracted Multireference Electron Correlation Methods
• A nonorthogonal state-interaction approach for matrix product state wave functions
• Relativistic EOM-CCSD for core-excited and core-ionized state energies based on the 4-component Dirac-Coulomb(-Gaunt) Hamiltonian
• Coordinate descent full configuration interaction
• Accurate many-body electronic structure near the basis set limit: application to the chromium dimer
• Perturbational treatment of spin-orbit coupling for generally applicable high-level multi-reference methods
• Large-scale relativistic complete active space self-consistent field with robust convergence
• Relativistic equation-of-motion coupled-cluster method using open-shell reference wavefunction
• Towards DMRG-tailored coupled cluster method in the 4c-relativistic domain

Cited by in corpus (3)

• A comparison between the one- and two-step spin-orbit coupling approaches based on the ab initio Density Matrix Renormalization Group
• Towards accurate spin-orbit splittings from relativistic multireference electronic structure theory
• Time-reversal symmetry adaptation in relativistic density matrix renormalization group algorithm