高压下铌铁矿相TiO_2直接相变的第一性原理研究  

First-principles study of direct phase transition of columbite TiO_2 under high pressure

作　　者：董海宽[1,2] 齐义辉[2] 高亚军[1] 修晓明[1] 史力斌[1] 

机构地区：[1]渤海大学数理学院,锦州121013 [2]辽宁工业大学材料科学与工程学院,锦州121001

出　　处：《原子与分子物理学报》2017年第4期689-695,共7页Journal of Atomic and Molecular Physics

基　　金：国家自然科学基金(11271055;11674037);辽宁省教育厅一般项目(20140445)

摘　　要：利用第一性原理的GGA+U方法对TiO_2的金红石相、铌铁矿相、萤石相、黄铁矿相和四方P42/nmc相进行了计算.首先,优化了这几个相的晶体结构及相关参数,分析了焓曲线图,发现了在50.1GPa压强下,铌铁矿相突然直接转变成一个新的四方P42/nmc相.其次,通过GGA+U和HSE06两种方法计算讨论了四方P42/nmc相的能带结构,并拟合分析了三阶B-M状态方程和XRD图谱.最后,通过分析相变压强范围、体弹模量和XRD图谱,本文认为四方P42/nmc相与立方萤石相是共存的,能很好符合2004年立方TiO_2的实验结果 .The GGA ＋ U method based on the first principles is used to calculate the rutile, columbite, fluorite, pyrite, and P42/nmc TiO2 phases. Firstly, the crystal structure of these phases are optimized and the related pa- rameters are obtained. The enthalpy curves are analyzed. It is found that the columbite can directly change to a tetragonal P42/nmc structure under 50. 1 GPa pressure. Secondly, the energy band structures of the P42/nmc TiO2 are calculated and discussed by GGA ＋ U and HSE06 methods. The third - order Birch - Murnaghan equa- tion of state and the XRD spectra are fitted and analyzed. Finally, it is thought that fluorite and P42/nmc may be coexisting phases, which is in accordance with the experimental results of the pressure range, bulk modulus and XRD spectra of cubic TiO2.

关 键 词：第一性原理 TIO2 相变 四方P42/nmc TIO2 

分 类 号：O521[理学—高压高温物理]