One-Step Relativistic Driven Similarity Renormalization Group Multireference Perturbation Theory

TL;DR

This paper introduces an efficient relativistic multireference perturbation theory method that accurately captures spin--orbit effects in strongly correlated systems with high computational efficiency.

Contribution

The authors develop and demonstrate a one-step relativistic multireference perturbation theory based on the X2C Hamiltonian, improving accuracy and efficiency for strongly correlated systems.

Findings

Achieves spin--orbit splittings with less than 7% mean absolute percentage error.

Accurately captures SOC effects in systems with elements up to the sixth row.

Has a computational scaling of fifth power in system size.

Abstract

We present an efficient implementation of a one-step relativistic second-order multireference perturbation theory based on the multireference driven similarity renormalization group (MR-DSRG) using the exact two-component (X2C) Hamiltonian, which we denote X2C-DSRG-MRPT2. We show that the X2C-DSRG-MRPT2 method can accurately capture spin--orbit coupling (SOC) effects in the electronic structure of strongly correlated systems containing elements across the periodic table. We further demonstrate that the X2C-DSRG-MRPT2 method, through its variational treatment of SOC effects, can yield spin--orbit splittings with mean absolute percentage errors consistently below 7% with respect to experimental values for systems containing up to sixth row elements. With its modest computational scaling (fifth power in system size) and high accuracy, X2C-DSRG-MRPT2 provides a promising avenue for the routine treatment of relativistic effects in strongly correlated molecular systems.