A Quantum Monte Carlo study of the structural, energetic, and magnetic properties of two-dimensional (2D) H and T phase VSe${}_2$

Abstract

Previous works have controversially claimed near-room temperature ferromagnetism in two-dimensional (2D) VSe${}_2$, with conflicting results throughout the literature. These discrepancies in magnetic properties between both phases (T and H phase) of 2D VSe${}_2$ are most likely due to the structural parameters being coupled to the magnetic properties. Specifically, both phases have a close lattice match and similar total energies, which makes it difficult to determine which phase is being observed experimentally. In this study, we used a combination of density functional theory (DFT), highly accurate diffusion Monte Carlo (DMC) and a surrogate Hessian line-search optimization technique to resolve the previously reported discrepancy in structural parameters and relative phase stability. With DMC accuracy, we determined the freestanding geometry of both phases and constructed a phase diagram. Our findings demonstrate the successes of the DMC method coupled with the surrogate Hessian structural optimization technique when applied to a 2D magnetic system.

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Cited by in corpus (4)

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• Basis set incompleteness errors in fixed-node diffusion Monte Carlo calculations on non-covalent interactions
• Toward improved property prediction of 2D materials using many-body quantum Monte Carlo methods
• Quantum Monte Carlo and density functional theory study of strain and magnetism in 2D 1T-VSe${}_2$ with charge density wave states