Study of LaScO₃ by electronic structure quantum Monte Carlo methods

Transition Metal Oxide perovskites (ABO3) are a set of materials that have been widely studied due to the coupling of their charge, spin, orbital, and lattice degrees of freedom, leading to a variety of interesting properties. These materials are typically studied with DFT+U, hybrids, or GW methods to correct for the self-interaction errors within DFT, typically due to the localized nature of the occupied d-orbitals and are often further complicated by various magnetic states. However, even in cases where there is no d-occupancy and the material is a non-magnetic insulator, such as LaScO₃, there can be significant errors from these methods due to inaccuracies in the description of electron correlation. For example, the GW methods underestimate the bandgap by roughly 1.5 eV, and hybrid DFT must be tuned in order to reproduce the bandgap. Here, we present a study of LaScO3 using the highly accurate Fixed-Node Diffusion Monte Carlo (FNDMC) method. We show that by carrying out the standard FNDMC methodology, we are able to accurately reproduce the experimental bandgap of LaScO3 without any parameter tuning as is required by DFT and related methods. Additionally, we present calculations of the cohesive energy, equation of state, and other properties using FNDMC.