Critical point between the microscopic and macroscopic two-dimensional materials

Abstract

The boundary between microscopic and macroscopic worlds has long attracted significant attention. In this study the growth of 2D materials, graphene, h-BN, siligraphene, quadrilateral MgO and LiF from their smallest structural units are simulated at the B3LYP/6-31g(d) level and the average areas of inner and outermost units of these systems are calculated. It is found that the variation of the average area difference between inner and outermost units with the increase of radius R becomes gradually smaller and smaller. This implies that there may exist a critical point between the microscopic and macroscopic 2D materials. It is assumed that this critical point may be related to the inflection point of the curve of the average area difference versus the radius R. Five critical points of these 2D materials are determined. The corresponding radii are ranged from 0.731 nm of planar LiF to 1.907 nm of graphene. They are comparable to the size of critical points in pure liquid compounds reported in literature.It is expected that the data of critical points presented in this study may provide some guidance for the related experimental works in the future.