Optical properties of a diamond NV color center from capped embedded multiconfigurational correlated wavefunction theory

TL;DR

This paper demonstrates that capped density functional embedding theory combined with multiconfigurational perturbation theory accurately predicts the optical excitation energies of diamond NV centers, offering a robust and size-independent computational approach.

Contribution

The study introduces a novel application of capped-DFET with multiconfigurational perturbation theory to model diamond NV centers, achieving high accuracy and size independence.

Findings

Reproduces excitation energies with errors < 0.1 eV

Predicts properties independently of cluster size

Reduces dependence on supercell size for charged defects

Abstract

Diamond defects are among the most promising qubits. Modelling their properties through accurate quantum mechanical simulations can further their development into robust units of information. We use the recently developed capped density functional embedding theory (capped-DFET) with the multiconfigurational n-electron valence second-order perturbation theory to characterize the electronic excitation energies for different spin manifolds of the well-characterized negatively charged substitutional N defect adjacent to a vacancy (V$_C$) in diamond (N$_C$V$_C^-$). We successfully reproduce vertical excitation energies for both triplet and singlet states of N$_C$V$_C^-$ with errors < 0.1 eV. Unlike other embedding methods, capped-DFET exhibits robust predictions that are approximately independent of the embedded cluster size: it only requires a cluster to contain the defect atoms and their nearest neighbors (as small as a 40-atom capped cluster). Furthermore, our method is free from slowly converging Coulomb interactions between charged defects, and thus also only weakly dependent on supercell size.