Spin decontamination for magnetic dipolar coupling calculations: Application to high-spin molecules and solid-state spin qubits

TL;DR

This paper introduces a new method to correct spin contamination in density functional theory calculations, improving the accuracy of magnetic coupling and zero-field splitting energies in high-spin molecules and solid-state spin qubits.

Contribution

The authors develop a robust correction strategy for spin contamination applicable to both periodic and finite systems, enhancing the reliability of magnetic property calculations.

Findings

Reduces dependence on exchange-correlation functionals

Accurately predicts zero-field splitting in spin qubits

Validates correction method on high-spin molecules

Abstract

An accurate description of the two-electron density, crucial for magnetic coupling in spin systems, provides in general a major challenge for density functional theory calculations. It affects, e.g., the calculated zero-field splitting (ZFS) energies of spin qubits in semiconductors that frequently deviate significantly from experiment. In the present work (i) we propose an efficient and robust strategy to correct for spin contamination in both extended periodic and finite-size systems, (ii) verify its accuracy using model high-spin molecules, and finally (iii) apply the methodology to calculate accurate ZFS of spin qubits (NV$^-$ centers, divacancies) in diamond and silicon carbide. The approach is shown to reduce the dependence on the used exchange-correlation functional to a minimum.