Structure and electronic properties of transition-metal/Mg bimetallic clusters at realistic temperatures and oxygen partial pressures

TL;DR

This study investigates the composition, structure, and electronic properties of transition-metal/Mg oxide clusters under realistic conditions, revealing that oxygen content influences electronic properties more than the specific transition metal present.

Contribution

The paper introduces a comprehensive ab initio thermodynamics approach combined with genetic algorithms to analyze cluster properties at realistic temperatures and pressures, challenging traditional views on metal influence.

Findings

Electronic gap strongly affected by Mg-coordinated O2

Transition metal type has limited impact on electronic properties

Oxygen content correlates with reactivity more than metal type

Abstract

Composition, atomic structure, and electronic properties of TM$_x$Mg$_y$O$_z$ clusters (TM = Cr, Ni, Fe, Co, $x+y \leq 3$) at realistic temperature $T$ and partial oxygen pressure $p_{\textrm{O}_2}$ conditions are explored using the {\em ab initio} atomistic thermodynamics approach. The low-energy isomers of the different clusters are identified using a massively parallel cascade genetic algorithm at the hybrid density-functional level of theory. On analyzing a large set of data, we find that the fundamental gap E$_\textrm{g}$ of the thermodynamically stable clusters are strongly affected by the presence of Mg-coordinated O$_2$ moieties. In contrast, the nature of the transition metal does not play a significant role in determining E$_\textrm{g}$. Using E$_\textrm{g}$ of a cluster as a descriptor of its redox properties, our finding is against the conventional belief that the transition metal plays the key role in determining the electronic and therefore chemical properties of the clusters. High reactivity may be correlated more strongly with oxygen content in the cluster than with any specific TM type.