Correlated High-Pressure Phase Sequence of VO 2 under Strong Compression

• Published in: The journal of physical chemistry letters Vol. 9; no. 9; pp. 2388 - 2393
• Main Authors: Xie, Sheng-Yi, Wang, Luhong, Liu, Fuyang, Li, Xian-Bin, Bai, Ligang, Prakapenka, Vitali B., Cai, Zhonghou, Mao, Ho-kwang, Zhang, Shengbai, Liu, Haozhe
• Format: Journal Article
• Language: English
• Published: United States 03.05.2018
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.8b00771

Understanding how the structures of a crystal behave under compression is a fundamental issue both for condensed matter physics and geoscience. Traditional description of crystal as the stacking of unit-cell with special symmetry has gained much success on the analysis of physical properties. Unfortunately, it's hard to reveal the relationship between the compressed phases. Taking the family of metal dioxides (MO2) as an example, the structural evolution, subject to fixed chemical formula and highly confined space, often appears as a set of random and uncorrelated events. Here we provide an alternative way to treat the crystal as the stacking of the coordination polyhedron and then discover a unified structure transition pattern in our case VO2. X-ray diffraction (XRD) experiment and first-principles calculation show that the coordination increase happens only at one apex of the V-centered octahedron in an orderly fashion, leaving the base plane and the other apex topologically intact. The polyhedron evolve towards the way to increase their sharing, indicating a general rule for the chemical bonds of MO2 to give away the ionicity in exchange for covalency under pressure.