金红石相Fe^(3+)/TiO_2结构与磁特性分子动力学模拟

Structure and magnetism of Fe^(3+)/TiO_2-rutile using molecular dynamics simulation

结合共价作用与量子修正,采用分子动力学方法,模拟计算了300 K常压下金红石相Fe3+/TiO2晶体结构及能量参数.结果表明,当掺杂量达5.7 mol%时,晶胞参数a与晶胞体积明显增大,八面体共棱部分消失,(110)晶面中的阴离子精细结构逐渐消失,阴离子均方位移与体系能量也明显增大.此外,结构畸变易形成氧空位桥基团(Fe3+-[F心]-Ti4+),而使体系呈铁磁性,随掺杂量增加,该基团取向变化而易形成反铁磁性,所获得的模拟结果与磁特性与实验结果基本一致.

Molecular dynamics （MD） simulations with covalent interaction and quantum correction were performed on Fe^3＋/TiO2-rutile at 300 K and 101 kPa, and details of structural properties and energy parameters were presented. It was found that as the dopant amount of Fe^3 ＋ ions is up to 5.7 mol% , the cell parameter （a） and cell volume increase obviously, the sharing edges of octahedra and anionic fine structures of crystal plane （110） disappear gradually, and also the mean-square displacement （MSD） of anions and lattice energy enhance abruptly. In addition, the ferromagnetism for Fe^3 ＋/TiO2 occurs due to the formation of an oxygen - vacancy bridge group （Fe^3＋ -[ F center] -Ti^4＋） caused by structure distortion. With increasing of doping amount, the orientation of groups is in inhomogeneous and the antiferromagnetism for Fe^3＋/TiO2 forms. These results obtained by MD are consistent with the experimental observation.