Zero-Field Splitting Calculations by Multiconfiguration Pair-Density Functional Theory

Area of Science:

• Quantum chemistry
• Computational magnetism
• Materials science

Background:

• Zero-field splitting (ZFS) is crucial for single-molecule magnets (SMMs), electron paramagnetic resonance (EPR), and quantum computing.
• Accurate prediction of ZFS parameters is essential for designing novel SMMs.
• Including external correlation in multiconfigurational open-shell systems for magnetic property prediction presents a significant challenge.

Purpose of the Study:

• To develop a computationally efficient method for accurate ZFS parameter prediction.
• To address the challenge of incorporating external correlation in open-shell systems.
• To provide a powerful tool for the rational design of new SMMs.

Main Methods:

• Spin-orbit-inclusive multiconfiguration and multistate pair-density functional theory (MC-PDFT) calculations were employed.
• The method achieves a computational cost comparable to complete-active-space self-consistent field (CASSCF) theory.
• External correlation effects, crucial for magnetic properties, are included.

Main Results:

• A combination of compressed-state multistate MC-PDFT and weighted-state-averaged CASSCF optimized orbitals yields accurate ZFS results.
• The developed approach effectively includes correlation external to the active space.
• The computational cost remains manageable, similar to CASSCF.

Conclusions:

• The presented spin-orbit-inclusive MC-PDFT approach offers a computationally feasible and accurate method for predicting ZFS.
• This method advances the design of SMMs and other magnetic materials.
• It overcomes limitations of previous methods requiring expensive multireference perturbation theory.