## Dissertations, Theses, and Masters Projects

2020

Dissertation

#### Degree Name

Doctor of Philosophy (Ph.D.)

Physics

Henry Krakauer

Shiwei Zhang

Mumtaz Qazilbash

Marc Sher

#### Committee Member

Andreas Stathopoulos

#### Abstract

Upon cooling past a critical temperature $T_\mathrm{c}=\SI{340}{K}$ Vanadium dioxide (VO$_2$) exhibits a metal-insulator transition (MIT) from a metallic rutile R to an insulating monoclinic M1 phase. Other insulating phases, a monoclinic M2 and triclinic T, have been identified and are accessible via strain or doping. Despite decades of research, the nature of the VO$_2$ MIT is still not fully understood. In this work we present ab-initio hybrid density functional theory (DFT) calculations on the insulating phases, compare the results to experimental measurements and discuss their implications on our understanding of the VO$_2$ MIT. Recent measurements on M1 VO$_2$ under high pressure found a transition to a metallic monoclinic state X at $P_\mathrm{c}=\SI{34.3}{GPa}$. Following this increased interest in the study of VO$_2$ at high pressures, we will also present results of hybrid-DFT calculations on the M1 phase under increasing pressure. Our calculations predict that M1 may become metallic above $\sim\SI{32}{GPa}$, in good agreement with experiment.

#### DOI

http://dx.doi.org/10.21220/s2-8znr-g633

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