Density Functional Studies Reveal Anomalous Lattice Behavior in Metal Cyanide, AgC8N5

TL;DR

This study uses density functional theory to uncover unusual lattice behaviors in AgC8N5, including negative linear compressibility and thermal expansion along the c-axis, driven by silver atom dynamics.

Contribution

It reveals the role of van der Waals interactions and atom dynamics in the anomalous lattice responses of AgC8N5 under pressure and temperature.

Findings

Negative linear compressibility along c-axis

Large negative thermal expansion along c-axis

Silver atom dynamics govern lattice anomalies

Abstract

We have investigated anomalous lattice behavior of metal organic framework compound AgC8N5on application of pressure and temperature using ab-initio density functional theory calculations. The van der Waals dispersion interactions are found to play an important role in structural optimization and stabilization of this compound. Our ab-initio calculations show negative linear compressibility (NLC) along the c-axis of the unit cell. The ab-initio lattice dynamics as well as the molecular dynamics simulations show large negative thermal expansion (NTE) along the c-axis. The mechanism of NLC and NTE along the c-axis of the structure is governed by the dynamics of Ag atoms in the a-b plane. The NLC along the c-axis drives the NTE along that direction.