title: Density and structural effects in the radiation tolerance of TiO₂ polymorphs.
abstract: 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.
authors.affiliation: Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Qin
authors.forename: E Y
authors.initials: EY
authors.lastname: Kuo
authors.forename: K R
authors.initials: KR
authors.lastname: Whittle
authors.forename: S C
authors.initials: SC
authors.lastname: Middleburgh
authors.forename: M
authors.initials: M
authors.lastname: Robinson
authors.forename: N A
authors.initials: NA
authors.lastname: Marks
authors.forename: G R
authors.initials: GR
authors.lastname: Lumpkin
mesh_terms: D003198:Computer Simulation; D020450:Heavy Ions; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation / Q000528:radiation effects; D011829:Radiation Dosage; D013314:Stress, Mechanical; D013696:Temperature; D014025:Titanium / Q000737:chemistry* / Q000528:radiation effects*
chemical_list: C009495:titanium dioxide; D014025:Titanium