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

We have investigated anomalous lattice behavior of metal organic framework compound AgC8N5 on 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 and 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.