V5+掺杂TiO2金红石结构的分子动力学

采用经典离子晶体相互作用势模型， 进行量子化修正，对TiO2金红石相替位式掺杂0.5mol％V5+进行分子动力学模拟，计算了常温常压下的键长、键角的分布函数，分析了晶体的微结构变化以及V5+对TiO6八面体的影响．模拟结果表明，掺杂V5+会导致Ti-O、O-O键长以及O-Ti-O键角的分布范围变宽，其中，键长的主峰位置未发生显著的移动， 而键角主峰向低角度方向移动． 由于V5+比Ti4+有较高的正电荷和较小的离子半径， 因此V5+向氧八面体间空隙扩散，且掺杂V5+迁移出原来的O6八面体，从而导致空隙邻近的TiO6八面体发生严重扭曲．在低掺杂情况下(0.5 mol％)虽然掺杂易造成结构畸变，但模拟体系整体仍维持金红石结构；所得模拟的键长变化、掺杂V5+迁移、晶相等结构特性与FTIR、Raman、XRD、ESR等实验结果相一致．

Characterization of V5+/TiO2-Rutile Using Molecular Dynamics Simulations

Molecular dynamics (MD) simulations with a quantum correction were used to study the 0.5 mol% V5+/TiO2 rutile under conditions of 300 K and 101 kPa. The interatomic potential function in MD simulations is composed of Coulomb, short-range repulsion, van der Waals, and Morse interactions. The topology of rutile was found to undergo a large deformation when Ti4+ is replaced by V5+, which can be related to the difference of valence and ionic radius between V5+ and Ti4+. The graphed distributions of Ti-O and O-O bond lengths, and O-Ti-O angles are all broaden. The simulations showed that when Ti4+ is replaced by V5+, the V5+ moves out of the O6 polyhedron and toward the interstice between TiO6 octahedra, which results in serious distortion of the octahedra near the interstice, but the phase with 0.5 mol% V5+ doping still remains in rutile. The structural features, such as the bond lengths, migration of the dopant, and crystal phase in the MD simulation are consistent with the experimental observations by FTIR, Raman, XRD and ESR.