Stability and electronic structure of the complex K$_2$PtCl$_6$ structure-type hydrides

TL;DR

This study uses first-principles calculations to analyze the stability, bonding, and electronic structure of K2PtCl6-type hydrides, revealing ionic dominance, ligand field effects, and potential ferroelectric properties relevant for hydrogen storage.

Contribution

It provides new insights into the bonding, electronic structure, and potential ferroelectricity of complex hydrides with K2PtCl6 structure type using density functional theory.

Findings

Cohesion mainly ionic with ligand field effects

Potential ferroelectricity in Pb2RuH6 and Be2FeH6

Implications for hydrogen storage applications

Abstract

The stability and bonding of the ternary complex K$_2$PtCl$_6$ structure hydrides is discussed using first principles density functional calculations. The cohesion is dominated by ionic contributions, but ligand field effects are important, and are responsible for the 18-electron rule. Similarities to oxides are discussed in terms of the electronic structure. However, phonon calculations for Sr$_2$RuH$_6$ also show differences, particularly in the polarizability of the RuH$_6$ octahedra. Nevertheless, the yet to be made compounds Pb$_2$RuH$_6$ and Be$_2$FeH$_6$ are possible ferroelectrics. The electronic structure and magnetic properties of the decomposition product, FeBe$_2$ are reported. Implications of the results for H storage are discussed.