One-step treatment of spin-orbit coupling and electron correlation in large active spaces

Abstract

In this work we demonstrate that the heat bath configuration interaction (HCI) and its semistochastic extension can be used to treat relativistic effects and electron correlation on an equal footing in large active spaces to calculate the low energy spectrum of several systems including halogens group atoms (F, Cl, Br, I), coinage atoms (Cu, Au) and the Neptunyl(VI) dioxide radical. This work demonstrates that despite a significant increase in the size of the Hilbert space due to spin symmetry breaking by the spin-orbit coupling terms, HCI retains the ability to discard large parts of the low importance Hilbert space to deliver converged absolute and relative energies. For instance, by using just over $10^7$ determinants we get converged excitation energies for Au atom in an active space containing (150o,25e) which has over $10^{30}$ determinants. We also investigate the accuracy of five different two-component relativistic Hamiltonians in which different levels of approximations are made in deriving the one-electron and two-electrons Hamiltonians, ranging from Breit-Pauli (BP) to various flavors of exact two-component (X2C) theory. The relative accuracy of the different Hamiltonians are compared on systems that range in atomic number from first row atoms to actinides.

18 pages, 3 figures, 3 tables

References in corpus (12)

• 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
• An adaptive configuration interaction approach for strongly correlated electrons with tunable accuracy
• Cheap and near exact CASSCF with large active spaces
• Excited states using semistochastic heat-bath configuration interaction
• Hybrid stochastic-deterministic calculation of the second-order perturbative contribution of multireference perturbation theory
• Four-Component Density Matrix Renormalization Group
• Multireference linearized Coupled Cluster theory for strongly correlated systems using Matrix Product States
• Relativistic Internally Contracted Multireference Electron Correlation Methods
• A nonorthogonal state-interaction approach for matrix product state wave functions
• Perturbational treatment of spin-orbit coupling for generally applicable high-level multi-reference methods
• Using CIPSI nodes in diffusion Monte Carlo

Cited by in corpus (16)

• Recent developments in the PySCF program package
• Fast Semistochastic Heat-Bath Configuration Interaction
• Excited States of Methylene, Polyenes, and Ozone from Heat-Bath Configuration Interaction
• Perspective: Essentials of Relativistic Quantum Chemistry
• Almost exact energies for the Gaussian-2 set with the semistochastic heat-bath configuration interaction method
• Multireference configuration interaction and perturbation theory without reduced density matrices
• State-Specific Coupled-Cluster Methods for Excited States
• SOiCI and iCISO: Combining iterative configuration interaction with spin-orbit coupling in two ways
• Ground- and Excited-State Dipole Moments and Oscillator Strengths of Full Configuration Interaction Quality
• Reference Vertical Excitation Energies for Transition Metal Compounds
• A comparison between the one- and two-step spin-orbit coupling approaches based on the ab initio Density Matrix Renormalization Group
• Consistent Second-Order Treatment of Spin-Orbit Coupling and Dynamic Correlation in Quasidegenerate N-Electron Valence Perturbation Theory
• Simulating Spin-Orbit Coupling With Quasidegenerate N-Electron Valence Perturbation Theory
• Ab initio Calculations in Atoms, Molecules, and Solids, Treating Spin-Orbit Coupling and Electron Interaction on Equal Footing
• Full Breit Hamiltonian in the Multiwavelets Framework
• Non-perturbative Many-Body Treatment of Molecular Magnets