Prevalence of pretransition disordering in the rutile-to- CaCl2 phase transition of GeO2

G. Alexander Smith, Daniel Schacher, Jasmine K. Hinton, Daniel Sneed, Changyong Park, Sylvain Petitgirard, Keith V. Lawler, Ashkan Salamat

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2 Scopus citations

Abstract

The ability to tailor a material's electronic properties using density driven disordering has emerged as a powerful route to materials design. The observation of anomalous structural and electronic behavior in the rutile to CaCl2 phase transition in SnO2 led to the prediction that such behavior is inherent to all oxides experiencing such a phase transition sequence [Smith et al., J. Phys. Chem. Lett. 10, 5351 (2019)1948-718510.1021/acs.jpclett.9b01633]. Here, the ultrawide band gap semiconductor GeO2 is confirmed to exhibit anomalous behavior during the rutile to CaCl2 phase transition. A phase pure rutile GeO2 sample synthesized under high-pressure, high-temperature conditions is probed using synchrotron diffraction and x-ray and optical spectroscopy under high pressure conditions. Density functional theory calculations show that the enthalpic barrier to displacing an oxygen along the B1g librational mode decreases with pressure leading up to the rutile to CaCl2 phase transition. The band structure of the distorted state shows that such oxygen displacements form small polarons.

Original languageEnglish
Article number134107
JournalPhysical Review B
Volume104
Issue number13
DOIs
StatePublished - Oct 1 2021
Externally publishedYes

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