Title: Computational characterization of novel nanostructured materials: A case study of NiCl$_2$

Abstract: A computational approach combining dispersion-corrected density functional theory (DFT) and classical molecular dynamics is employed to characterize the geometrical and thermo-mechanical properties of a recently proposed 2D transition metal dihalide NiCl$_2$. The characterization is performed using a classical interatomic force field whose parameters are determined and verified through the comparison with the results of DFT calculations. The developed force field is used to study the mechanical response, thermal stability, and melting of a NiCl$_2$ monolayer on the atomistic level of detail. The 2D NiCl$_2$ sheet is found to be thermally stable at temperatures below its melting point of ~695 K. At higher temperatures, several subsequent structural transformations of NiCl$_2$ are observed, namely a transition into a porous 2D sheet and a 1D nanowire. The computational methodology presented through the case study of NiCl$_2$ can also be utilized to characterize other novel 2D materials, including recently synthesized NiO$_2$, NiS$_2$, and NiSe$_2$.