Diffusion quantum Monte Carlo study of halogen and chromium-halogen complexes*

Diffusion quantum Monte Carlo (DMC) has emerged as an accurate method to predict the structural, electronic, magnetic, and defect properties of strongly-correlated transition metal oxides. We are extending the application of DMC to layered materials with the formula CrX₃ (X = F, Cl, Br and I) which have potential spintronic and biomedical applications. In order to establish the accuracy of our theoretical predictions for CrX₃, we must first carefully examine and estimate all errors in DMC. The use of pseudopotentials, although necessary for large systems, introduces errors. In this work, we test the performance of two sets of DMC pseudopotentials for halogen and chromium-halogen complexes. Using validated pseudopotentials, we contribute to the understanding of structural and vibrational properties of CrF₂ and CrF₃ molecules.