Drastic changes in electronic, magnetic, mechanical and bonding properties from Zr2CoH5 to Mg2CoH5

TL;DR

This study uses ab initio calculations to reveal significant differences in electronic, magnetic, mechanical, and bonding properties between Zr2CoH5 and Mg2CoH5, despite their similar formulas and structures.

Contribution

The paper demonstrates how the environment of cobalt and the chemical nature of Zr versus Mg lead to contrasting properties in these hydrides, highlighting the role of local atomic environment.

Findings

Zr2CoH5 is more cohesive, harder, and less ductile than Mg2CoH5.

Zr2CoH5 exhibits metallic ferromagnetism due to non-bonding Co-dz2 states.

Mg2CoH5 is non-magnetic and insulating.

Abstract

Despite similarities in formulae and local structures of Zr2CoH5 and Mg2CoH5, they are shown from ab initio calculations to present contrasted electronic, magnetic, mechanical and bonding properties due to the environment of cobalt with hydrogen characterized by negatively charged CoHx entities (x = 4, 5 resp.) and to the chemical nature of Zr versus Mg. Zr2CoH5 is found more cohesive, harder and less ductile than Mg2CoH5. High density of states at the Fermi level arises from out-of-plane non-bonding Co-dz2 in Zr2CoH5 which is found metallic ferromagnet in the ground state, in contrast with non magnetic and insulating Mg2CoH5.