A DFT study of thermal and structural properties of 2D layers (Short
title: Two-Dimensional materials)
Abstract
Two-dimensional (2D) materials have exhibited exceptional properties
which meet the demands of future applications. These materials appeared
after discovery of graphene in 2004 offered such device grade
characteristics at nanoscale which did not appear on bulk scale. The
research turned to search alternate 2D materials when drawbacks of
graphene became surfaced. Despite significant successes and
unprecedented efforts which consequent upon several beyond-graphene 2D
materials, the complete potentials of such materials are still
unexplored which may restrict their usage in devices. This work was
carried out with motivation to investigate the thermal stability of
several 2D-mono-layered materials including graphene, Borophene,
Aluminene, Germanene, BN, SiC and MoS2 based on classical Molecular
Dynamics Simulations. Prior to the implementation of the conditions for
thermal calculations, the structures were optimized using
Geometry-Optimization method. It appeared that all the structural
parameters which includes lattice-constant, bond-length and dihedral
angles were precisely determined. On the contrary, it was found that
several materials beyond graphene can resist up-to certain temperature
ranges, depicting the material dependent thermal stability. The radial
distribution function (RDF) was calculated which pointed towards thermal
broadening, bond breakage and bond formation for the slabs. The
RDF-peaks were found to characterize the probability of finding any
particle in the nearest neighbors which extend the phenomenon of thermal
stability. Thermal stability was compared by plotting the temperature
and energy curves from which, the phase transition temperature and heat
capacity was determined for the slabs including graphene as benchmark.
The phase transition temperatures are found as 4510 K, 2273 K, 933 K,
1670 K, 3246 K, 4050 K, and 1460 K for graphene, Borophene, Aluminene,
Germanene, BN, SiC and MoS2 respectively. Besides the analysis of
temperature-energy variations, the thermal broadening is also determined
and discussed to examine the thermal-stability for usage of the
materials in high temperature applications.