Density and structural effects in the radiation tolerance of TiO2 polymorphs

• Published in: Journal of physics. Condensed matter 2013-09, Vol.25 (35), p.355402-355402
• Main Authors: Qin, M J, Kuo, E Y, Whittle, K R, Middleburgh, S C, Robinson, M, Marks, N A, Lumpkin, G R
• Format: Article
• Language: English
• Subjects: Computer Simulation; Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Heavy Ions; Ion radiation effects; Models, Chemical; Models, Molecular; Molecular Conformation - radiation effects; Physical radiation effects, radiation damage; Physics; Radiation Dosage; Solid-solid transitions; Specific phase transitions; Stress, Mechanical; Structure of solids and liquids; crystallography; Temperature; Titanium - chemistry; Titanium - radiation effects
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/25/35/355402

The radiation response of TiO2 has been studied using molecular dynamics. The simulations are motivated by experimental observations that the three low-pressure polymorphs, rutile, brookite and anatase, exhibit vastly different tolerances to amorphization under ion-beam irradiation. To understand the role of structure we perform large numbers of simulations using the small thermal spike method. We quantify to high statistical accuracy the number of defects created as a function of temperature and structure type, and reproduce all the main trends observed experimentally. To evaluate a hypothesis that volumetric strain relative to the amorphous phase is an important driving force for defect recovery, we perform spike simulations in which the crystalline density is varied over a wide range. Remarkably, the large differences between the polymorphs disappear once the density difference is taken into account. This finding demonstrates that density is an important factor which controls radiation tolerance in TiO2.