Generalized force field methodology for moiré heterostructures

In this work, a generalized force field methodology for the relaxation of large moiré heterostructures is proposed. The force field parameters are optimized to accurately reproduce the structural degrees of freedom of some small and manageable cells found using density functional theory (DFT). The parameters can then be used to tackle larger systems. We specialize to the case of transition-metal dichalcogenide (TMD) homo- and heterobilayers using a combination of the Stillinger-Weber (SW) intralayer- and the Kolmogorov-Crespi (KC) interlayer-potential. The results show excellent agreement in terms of band structure and effective masses between DFT and SW+KC force field relaxation. Using the relaxed structures, a simplified and systematic scheme for the extraction of moiré potential is presented. The results show the importance of in plane and out of plane relaxation effects on the moiré potential which is made both deeper and wider after relaxation. An interpolation based methodology for the calculation of the correct binding energy is also proposed. Finally, we glimpse into the formation rate of domains induced by atomic reconstruction, which can be managed with our force-field parametrization.