Observation of 9-Fold Coordinated Amorphous TiO₂ at High Pressure

Journal Article · Sun Dec 22 23:00:00 EST 2019 · Journal of Physical Chemistry Letters

DOI:https://doi.org/10.1021/acs.jpclett.9b03378· OSTI ID:1607480

Shu, Yu ^[1]; Kono, Yoshio ^[2]; Ohira, Itaru ^[2]; Li, Quanjun ^[3]; Hrubiak, Rostislav ^[1]; Park, Changyong ^[1]; Kenney-Benson, Curtis ^[1]; Wang, Yanbin ^[4]; Shen, Guoyin ^[1]

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1. Argonne National Lab. (ANL), Argonne, IL (United States). High Pressure Collaborative Access Team
2. Carnegie Inst. of Washington, Argonne, IL (United States)
3. Jilin Univ., Changchun (China). State Key Lab. of Superhard Materials
4. Univ. of Chicago, IL (United States). Center for Advanced Radiation Sources (CARS)

Knowledge of the structure in amorphous dioxides is important in many fields of science and engineering. In this paper, we report new experimental results of high-pressure polyamorphism in amorphous TiO₂ (a-TiO₂). Our data show that the Ti coordination number (CN) increases from 7.2 ± 0.3 at ~16 GPa to 8.8 ± 0.3 at ~70 GPa and finally reaches a plateau at 8.9 ± 0.3 at ≲86 GPa. The evolution of the structural changes under pressure is rationalized by the ratio ($$γ$$) of the ionic radius of Ti to that of O. It appears that the CN ≈ 9 plateau correlates with the two 9-fold coordinated polymorphs (cotunnite, Fe₂P) with different $$γ$$ values. This CN-$$γ$$ relationship is compared with those of a-SiO₂ and a-GeO₂, displaying remarkably consistent behavior between CN and $$γ$$. The unified CN-$$γ$$ relationship may be generally used to predict the compression behavior of amorphous AO₂ compounds under extreme conditions.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC02-06CH11357; FG02-99ER45775
• OSTI ID: 1607480
• Journal Information: Journal of Physical Chemistry Letters, Journal Name: Journal of Physical Chemistry Letters Journal Issue: 2 Vol. 11; ISSN 1948-7185
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Amorphous materials
Chemical structure
Compression
Crystal structure
Physical and chemical processes