Temperature dependent phase transition and negative thermal expansion of Hg2Cl2 compound: insights from first-principle DFT and Born-Oppenheimer on the fly molecular dynamics calculations

ABSTRACT The paper is aimed to understand the key phonon modes that are responsible for the temperature dependent structural phase transition and negative thermal expansion of Hg2Cl2 compound for the first time with the aid of density functional theory and Born-Oppenheimer on the fly molecular dynamics calculations. The phonon dispersion spectra, phonon density of states and Grüneisen parameters for the body-centered tetragonal and base-centered orthorhombic phases of the compound have been explored in detail. The order parameter associated with the phase transition and its nature has also been reported herewith. We believe that the present study will not only help for futuristic designs of improved functionalized systems with Hg2Cl2 compound but also can augment their applications in thermoelectric conversion systems, fibre-optic communications, thermal expansion compensators and in fuel cells.