The effect of van der Waals force on two-dimensional SiC/GeC heterostructures

The effect of van der Waals interaction on two-dimensional (2D) SiC/GeC heterostructures has been studied based on the density functional theory. The van der Waals interaction is considered by employing the semi-empirical correction scheme of Grimme [1], which is used in optimizing the equilibrium interlayer distance and binding energy between 2D monolayers. We found that for the layered SiC/GeC heterostructure with the C-Ge (Si-C) species order, the cohesive energy as a function of interlayer distance is about 0.03 eV per unit cell lower than that with the C-C (Si-Ge) species order, for both AA and AB stacking. Further findings show that the interlayer electrostatic forces mainly stabilize the equilibrium distance for the C-Ge (Si-C) species ordering, and vdW interactions only make the system attain a lower cohesive energy. On the other hand, vdW forces stabilize the interlayer distance for the C-C (Si-Ge) species order. These preliminary results suggest that interlayer electrostatic forces may play a role in ionic-like multilayer heterostructures.
[1] S. Grimme, J. Comput. Chem. 27, 1787 (2006)