Efficient Prediction of Highly Anisotropic Excitonic Properties in the Layered Antiferromagnet CrSBr via Time-Dependent Density Functional Theory.

CrSBr, a layered anisotropic van der Waals antiferromagnet, has recently emerged as a versatile platform where strong coupling between optical excitations and magnetic order enables magneto-optical control at low dimensions. While experiments have progressed rapidly, predictive and reliable ab initio descriptions remain limited to self-consistent, many-body perturbation theory, which is computationally expensive and technically challenging. Here, we present an alternative approach that accurately predicts the electronic and optical properties of CrSBr at substantially lower computational cost, while retaining quantitative accuracy in the coupling between excitons and magnetic order. Using a tuned hybrid density functional with on-site corrections, we reproduce fundamental and optical gaps and quantitatively capture the interaction between excitonic transitions and magnetic order. We then employ this functional to investigate excitonic shifts induced by spin canting that would result from applying an external magnetic field. Our results establish an efficient framework for modeling excitonic and magneto-optical phenomena in layered magnetic semiconductors.