This work centers around the evaluation of various computational DFT-based methods in their ability to correctly predict equilibrium lattice constants while at the same time producing reliable interaction energies for h-BN as a prime example of both a covalent as well as weakly bound system. The state-of-the-art fixed-node diffusion quantum Monte Carlo method provided a reference estimate of the bulk h-BN exfoliation energy.

Abstract

Materials that exhibit both strong covalent and weak van der Waals interactions pose a considerable challenge to many computational methods, such as DFT. This makes assessing the accuracy of calculated properties, such as exfoliation energies in layered materials like hexagonal boron nitride (h-BN) problematic, when experimental data are not available. In this paper, we investigate the accuracy of equilibrium lattice constants and exfoliation energy calculation for various DFT-based computational approaches in bulk h-BN. We contrast these results with available experiments and reference fixed-node diffusion quantum Monte Carlo (QMC) results. From our reference QMC calculation, we obtained an exfoliation energy of −33±$$ -33\pm $$2 meV/atom (-0.38±$$ \pm $$0.02 J/m2$$ {}^2 $$).