Systematic DFT+U and Quantum Monte Carlo Benchmark of Magnetic Two-Dimensional (2D) CrX₃ (X = I, Br, Cl, F)

Abstract

The search for two-dimensional (2D) magnetic materials has attracted a great deal of attention because of the experimental synthesis of 2D CrI 3 , which has a measured Curie temperature of 45 K. Often times, these monolayers have a higher degree of electron correlation and require more sophisticated methods beyond density functional theory (DFT). Diffusion Monte Carlo (DMC) is a correlated electronic structure method that has been demonstrated to be successful for calculating the electronic and magnetic properties of a wide variety of 2D and bulk systems, since it has a weaker dependence on the Hubbard parameter (U) and density functional. In this study, we designed a workflow that combines DFT +U and DMC in order to treat 2D correlated magnetic systems. We chose monolayer CrX 3 (X = I, Br, Cl, F), with a stronger focus on CrI 3 and CrBr 3 , as a case study due to the fact that they have been experimentally realized and have a finite critical temperature. With this DFT+U and DMC workflow and the analytical method of Torelli and Olsen, we estimated a maximum value of 43.56 K for the T c of CrI 3 and 20.78 K for the T c of CrBr 3 , in addition to analyzing the spin densities and magnetic properties with DMC and DFT+U. We expect that running this workflow for a well-known material class will aid in the future discovery and characterization of lesser known and more complex correlated 2D magnetic materials.

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Inverse Design of Next-Generation Superconductors Using Data-Driven Deep Generative Models

“…JARVIS (Joint Automated Repository for Various Integrated Simulations, ) is a collection of databases and tools to automate materials design using classical force-field, density functional theory, machine learning calculations, and experiments. JARVIS-DFT is a density functional theory based database of over 75,000 materials with several material properties such as formation energy, band gap with different levels of theory, solar-cell efficiency, topological spin–orbit coupling spillage, − elastic tensors, dielectric tensors, piezoelectric tensors, infrared and Raman spectra, electric field gradients, exfoliation energies, two-dimensional (2D) magnets, and bulk and 2D superconductors, all with stringent DFT-convergence setup . Our ALIGNN and CDVAE models were trained on the 1058 DFT calculations of superconducting properties presented in ref .…”

Theoretical Study on the Raman Effect Due to Magnons in Two-Dimensional Magnets

“…Density functional theory (DFT) calculations were conducted using the Vienna Ab initio Simulation Package (VASP). − The semilocal generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) was used in the calculations. The intra-atomic correlation among d-orbitals of Cr ions were taken into account using the DFT+U method with Hubbard U parameter set to 1 eV. , The calculation band gap is 1.20 eV, in good agreement with experiments . DFT calculations were carried out using the primitive cell of the monolayer and bilayer CrI 3 with a uniform 10 × 10 × 1 k -point mesh and a 15 A vacuum.…”