Naicker Pavan K, Cummings Peter T, Zhang Hengzhong, Banfield Jillian F
Department of Chemistry, University of Cape Town, Private Bag Rondebosch, Cape Town, 7701, South Africa.
J Phys Chem B. 2005 Aug 18;109(32):15243-9. doi: 10.1021/jp050963q.
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.
报道了二氧化钛纳米颗粒在三种常见晶相（锐钛矿、板钛矿和金红石）中的分子动力学模拟。研究了由纳米颗粒的模拟X射线衍射图谱推断出的结构性质。确定了钛-氧键长随尺寸、晶相和温度的变化关系，发现其取决于钛的配位环境，而与晶相和尺寸无关。对于四配位钛离子，平衡Ti-O键长为1.86埃；对于五配位钛离子，为1.92埃；对于八面体钛离子，为1.94埃。由于表面积与体积比更大，较小的纳米颗粒具有更高比例的四配位和五配位钛离子。报道了锐钛矿、金红石和板钛矿颗粒的表面能。随着颗粒变大，纳米颗粒的表面能增加并趋近于一个恒定值。小尺寸金红石颗粒的表面能高于类似尺寸的锐钛矿颗粒，这与锐钛矿是纳米晶二氧化钛更稳定的相相一致。
