Influence of germanium substitution on the structural and electronic stability of the competing vanadium dioxide phases

TL;DR

This study uses density-functional theory to investigate how germanium doping affects the structural and electronic properties of vanadium dioxide, providing insights into the increased metal-insulator transition temperature.

Contribution

It offers a detailed DFT analysis of Ge-doped VO₂, revealing how Ge influences phase stability and transition behavior, which was not previously understood.

Findings

Ge doping perturbs metallic rutile phase

Induces structural distortions similar to insulating phase

Suggests explanation for increased transition temperature

Abstract

We present a density-functional theory (DFT) study of the structural, electronic, and chemical bonding behaviour in germanium (Ge)-doped vanadium dioxide (VO$_2$). Our motivation is to explain the reported increase of the metal-insulator transition temperature under Ge doping and to understand how much of the fundamental physics and chemistry behind it can be captured at the conventional DFT level. We model doping using a supercell approach, with various concentrations and different spatial distributions of Ge atoms in VO$_2$. Our results suggest that the addition of Ge atoms strongly perturbs the high-symmetry metallic rutile phase and induces structural distortions that partially resemble the dimerization of the experimental insulating structure. Our work, therefore, hints at a possible explanation of the observed increase in transition temperature under Ge doping, motivating further studies into understanding the interplay of structural and electronic transitions in VO$_2$.