Oxygen vacancies in vanadium dioxide: A DFT$+V$ study

TL;DR

This study uses DFT+V calculations to investigate how oxygen vacancies affect the structural and electronic properties of VO2, revealing that vacancies induce local distortions but can turn the M1 phase metallic through doping effects.

Contribution

It introduces a DFT+V approach to analyze oxygen vacancies in VO2, clarifying their role in the metal-insulator transition and electronic structure modifications.

Findings

Oxygen vacancies cause local distortions in VO2 M1 phase.

Vacancies lead to metallic behavior via doping effects.

The dimerization in M1 phase persists despite vacancies.

Abstract

We present a density-functional theory study of the effects of oxygen vacancies on the structural and electronic properties of vanadium dioxide (VO$_2$). Our motivation is the reported suppression of the metal-insulator transition by oxygen vacancies and the lack of a clear consensus on its origin. We use the DFT$+V$ method with a static intersite vanadium-vanadium interaction term, $V$, to calculate the properties of the oxygen-deficient metallic rutile and insulating monoclinic M1 phases of VO$_2$ on the same footing. We find that oxygen vacancies induce local distortions in the M1 phase, but do not destroy the dimerization usually associated with the insulating behavior. In spite of this, we find that the M1 phase becomes metallic as a result of the partial filling of the conduction band due to a rigid-band-like doping effect.