Stacking in Bulk and Bilayer Hexagonal Boron Nitride

The stacking orders in layered hexagonal boron nitride bulk and bilayers are studied using high-level ab initio theory [local second-order M\o{}ller-Plesset perturbation theory (LMP2)]. Our results show that both electrostatic and London dispersion interactions are responsible for interlayer distance and stacking order, with $A{A}^{\ensuremath{'}}$ being the most stable one. The minimum energy sliding path includes only the $A{A}^{\ensuremath{'}}$ high-symmetry stacking, and the energy barrier is 3.4 meV per atom for the bilayer. State-of-the-art density functionals with and without London dispersion correction fail to correctly describe the interlayer energies with the exception of a Perdew-Burke-Ernzerhof functional intended for solid state and surface systems that agrees very well with our LMP2 results and experiment.