High pressure phonon analysis of KMn(Ag(CN)₂)₃ single crystals studied by Raman Spectroscopy and first-principles calculations

Thermal expansion of solids is a physical property that depends on the nature of the interatomic potentials. Thermal expansion of a diatomic molecule can be explained based on the asymmetric shape of a typical interatomic potential well. On a macroscopic scale, normally all dimensions of a solid should increase with rise in temperature and on a microscopic scale we expect the energy of vibrational modes to increase with temperature giving rise to an increase in amplitude of vibrations. In this article, colossal thermal expansion of KMnAg₃(CN)₆ has been discussed. Detailed analysis of nature of phonon modes contributing to colossal thermal expansion, negative linear compressibility and pressure induced phase transformations are explained using results obtained from Raman spectroscopy and first principles calculations