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One-Step Relativistic Driven Similarity Renormalization Group Multireference Perturbation Theory.
Zijun Zhao1, Francesco A Evangelista1
1Department of Chemistry and Cherry Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, United States.
Journal of Chemical Theory and Computation
|July 10, 2026
Summary
We developed an efficient quantum chemistry method, X2C-DSRG-MRPT2, to accurately calculate spin-orbit coupling effects in complex molecules. This approach offers a reliable way to study relativistic phenomena in strongly correlated systems.
Area of Science:
- Quantum Chemistry
- Computational Physics
- Relativistic Effects
Background:
- Strongly correlated systems exhibit complex electronic structures.
- Relativistic effects, particularly spin-orbit coupling (SOC), significantly influence these systems.
- Accurate theoretical methods are needed to model these effects.
Purpose of the Study:
- To present an efficient implementation of a relativistic second-order multireference perturbation theory.
- To accurately capture spin-orbit coupling (SOC) effects in strongly correlated systems.
- To provide a computationally feasible method for routine treatment of relativistic effects.
Main Methods:
- Developed the exact two-component (X2C) Hamiltonian combined with multireference driven similarity renormalization group (MR-DSRG) perturbation theory.
- Implemented a one-step relativistic second-order multireference perturbation theory (MRPT2).
- The method is denoted as X2C-DSRG-MRPT2.
Main Results:
- X2C-DSRG-MRPT2 accurately captures SOC effects in electronic structures of systems with elements across the periodic table.
- Achieved mean absolute percentage errors below 7% for spin-orbit splittings compared to experimental values for systems up to the sixth row.
- Demonstrated variational treatment of SOC effects.
Conclusions:
- X2C-DSRG-MRPT2 offers a promising avenue for routine treatment of relativistic effects in strongly correlated molecular systems.
- The method exhibits modest computational scaling (fourth power in system size for the perturbative step).
- High accuracy and computational efficiency make it suitable for complex molecular studies.
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