Van der Waals interactions in molecules and solids from quantum Monte Carlo

Many materials of intense current interest are layered materials or molecules in which dispersive van der Waals interactions play a central role, for example CrI₃, WTe₂, phosphorene, graphene and and its allotropes. In these materials, the electronic properties depend sensitively on the interlayer separation and stacking. While commonly used density functional theory (DFT) methods work well for covalent bonding, they have difficulties capturing all aspects of van der Waals-bonded systems. The L7 molecular test set was designed specifically to highlight dispersive interactions [1]. We will compare results on L7 from highly accurate diffusion Monte Carlo simulations from those of DFT methods, including bonding energy but also charge densities, and also discuss these results in the context of layered van der Waals-bonded materials.
[1] R. Sedlak, T. Janowski, M. Pitonak, J. Rezac, P. Pulay, and P. Hobza, Journal of chemical theory and computation 9, 3364 (2013).