First-principles study of pressure-induced structural response in hBN-encapsulated van der Waals materials

We compared pressure-induced structural changes of free-standing van der Waals (vdW) materials with those of their hBN-encapsulated counterparts. Using density functional theory, we optimized structures of various bulk vdW materials including graphene, hBN, and transition-metal dichalcogenides, under uniaxial pressure applied perpendicular to layers. Free-standing structures were then constructed based on the optimized parameters, and the residual forces were computed. Our results show that, in the studied vdW materials, residual forces are localized to the outermost one or two atomic layers. When the target materials were encapsulated with hBN and optimized under pressure, the residual forces became more localized, and a sizable variation of structural parameters was induced compared to the bulk under the same pressure, while the inner layers remain nearly unchanged.