| Abstract Scope |
Measurements of elastic moduli are of fundamental value for detecting changes in structure and bonding in solids and for explaining trends in lattice thermal conductivity. The first part of this talk will focus on the effects of a supersonic phase transition - fundamentally an order disorder transition - in the layered CuCrX2 (X=S,Se,Te). The second part will explore the (GeSe)1−x−(AgBiSe2)x system, in which alloying transforms the structure from orthorhombic to rhombohedral to cubic rock-salt, with the latter being the thermodynamically stable at a high temperature. We found an anomalous increase in the elastic moduli upon the transition from the rhombohedral to the cubic rock salt structure, leading to an increase in thermal conductivity. DFT suggests that this stiffening is caused by the tendency of Ge to exhibit strongly expressed lone-pair orbitals, which switch from fully oriented in the rhombohedral phase to randomly oriented in the cubic phase. |