title: Characterization of titanium dioxide nanoparticles using molecular dynamics simulations.
abstract: Molecular dynamics simulations of titanium dioxide nanoparticles in the three commonly occurring phases (anatase, brookite, and rutile) are reported. The structural properties inferred by simulated X-ray diffraction patterns of the nanoparticles were investigated. The titanium-oxygen bond length as a function of size, phase, and temperature was determined and was found to be dependent on the coordination environment of the titanium and independent of phase and size. The equilibrium Ti-O bond length is 1.86 A for a four-coordinated titanium ion, 1.92 A for a five-coordinated titanium ion, and 1.94 A for an octahedral titanium ion. Smaller nanoparticles are characterized by a higher fraction of titanium ions that are four and five coordinated, due to the larger surface area-to-volume ratios. The surface energies for anatase, rutile, and brookite particles were reported. The surface energy of the nanoparticle increases and approaches a constant value as the particle gets bigger. The surface energies of small rutile particles are higher than that for anatase particles of a similar size, consistent with anatase being the more stable phase of nanocrystalline titanium dioxide.
authors.affiliation: Department of Chemistry, University of Cape Town, Private Bag Rondebosch, Cape Town, 7701, South Africa. pnaicker@science.uct.ac.za
authors.forename: Pavan K
authors.initials: PK
authors.lastname: Naicker
authors.forename: Peter T
authors.initials: PT
authors.lastname: Cummings
authors.forename: Hengzhong
authors.initials: H
authors.lastname: Zhang
authors.forename: Jillian F
authors.initials: JF
authors.lastname: Banfield