The Ag...Ag dispersive interaction and exotic physical properties of Ag3Co(CN)6

TL;DR

This study uses advanced DFT calculations including dispersive interactions to explain and predict the unique thermal and mechanical properties of Ag3Co(CN)6, revealing new exotic behaviors linked to weak Ag...Ag interactions.

Contribution

It demonstrates the critical role of dispersive interactions in accurately modeling Ag3Co(CN)6 and predicts novel physical phenomena related to its structural dynamics.

Findings

Dispersive interactions are essential for reproducing the material's properties.

Heat enhances negative linear compressibility.

Sign change in thermal expansion coefficient under pressure.

Abstract

We report a density functional theory (DFT) study of Ag3Co(CN)6, a material noted for its colossal positive and negative thermal expansion, and its giant negative linear compressibility. Here we explicitly include the dispersive interaction within the DFT calculation, and find that it is essential to reproduce the ground state, the high-pressure phase, and the phonons of this material; and hence essential to understand this material's remarkable physical properties. New exotic properties are predicted. These include heat enhancement of the negative linear compressibility, a large reduction in the coefficient of thermal expansion on compression with change of sign of the mode Grueneisen parameters under pressure, and large softening of the material on heating. Our results suggest that these are associated with the weak Ag...Ag dispersive interactions acting with an efficient hinging mechanism in the framework structure.