Computational study of antiferromagnetic and mixed-valent diamagnetic phase of AgF2: crystal, electronic and phonon structure and p-T phase diagram

TL;DR

This study uses computational methods to analyze the crystal, electronic, and phonon structures of AgF2's alpha and beta phases, revealing thermodynamic stability and phase behavior relevant to related materials.

Contribution

It provides the first detailed computational comparison of AgF2's alpha and beta phases, including their stability, electronic, and phonon properties, within a unified theoretical framework.

Findings

Alpha phase is thermodynamically favored over beta at all conditions.

Beta phase is dynamically stable over a broader pressure range.

The study relates AgF2 phases to similar compounds like NaCuO2.

Abstract

Crystal and electronic structure, lattice dynamics and thermodynamic stability of little known mixed valent diamagnetic AgIAgIIIF4 beta form of AgF2 is thoroughly examined for the first time and compared with well known antiferromagnetic AgIIF2 alpha form within the framework of Density Functional Theory based methods, phonon direct method and quasiharmonic approximation. Computed equations of state, bulk moduli, electronic densities of states, electronic and phonon band structures including analysis of optically active modes and p T phase diagram of the alpha/beta system are presented. This study demonstrates that alpha is thermodynamically preferred over beta at all temperatures and pressures of its existance but simultaneously beta is dynamically stable in much broader pressure range. The beta phase is discussed in broader context of isostructural ternary metal fluorides and isolectronic oxides including NaCuO2, the reference compound for existence of CuIII species in high temperature oxocuprate superconductors.