Determination of the high-pressure crystal structure of BaWO{sub 4} and PbWO{sub 4}
Determination of the high-pressure crystal structure of BaWO{sub 4} and PbWO{sub 4}
复制标题
DOI：
10.1103/physrevb.73.224103
复制
发表时间：
2006-02
影响因子：
3.7
通讯作者：
Daniel Errandonea;J. Pellicer-Porres;Alfredo Segura;C. Ferrer‐Roca;F. Manjón;Ravhi S. Kumar;O. Tscha
中科院分区：
文献类型：
--
作者：
Daniel Errandonea;J. Pellicer-Porres;Alfredo Segura;C. Ferrer‐Roca;F. Manjón;Ravhi S. Kumar;O. Tscha
我们报道了BaWO{sub4}和PbWO{sub4}在高达56 Gpa和24 Gpa压力下的角色散X射线衍射和X射线吸收近边结构的研究结果。发现BaWO{sub4}在7.1 GPa时经历了从四方白钨矿结构(在正常情况下是稳定的)到单斜闪锌矿结构的压力驱动相变，而PbWO{sub4}在9 GPa时也发生了同样的相变。我们观察到另一个单斜晶系的第二个转变，我们认为这是等结构相BaWO{sub4}-II和PbWO{sub4}-III(空间群P2{sub1}/n)的转变。我们还进行了从头算总能量计算，支持该结构在高压下在这两个化合物中的稳定性。理论计算还发现，随着压力的增加，白钨矿相在局部变得不稳定，并位移地转变为纤锌矿结构。然而，亚铁闪锌矿结构是亚稳定的，只有在动力学上抑制了向P2{sub1}/n相的转变时才能发生。我们在BaWO{sub4}中的实验表明，它在47 Gpa以上变得无定形。
We report the results of both angle-dispersive x-ray diffraction and x-ray absorption near-edge structure studies in BaWO{sub 4} and PbWO{sub 4} at pressures of up to 56 GPa and 24 GPa, respectively. BaWO{sub 4} is found to undergo a pressure-driven phase transition at 7.1 GPa from the tetragonal scheelite structure (which is stable under normal conditions) to the monoclinic fergusonite structure whereas the same transition takes place in PbWO{sub 4} at 9 GPa. We observe a second transition to another monoclinic structure which we identify as that of the isostructural phases BaWO{sub 4}-II and PbWO{sub 4}-III (space group P2{sub 1}/n). We have also performed ab initio total-energy calculations which support the stability of this structure at high pressures in both compounds. The theoretical calculations further find that upon increase of pressure the scheelite phases become locally unstable and transform displacively into the fergusonite structure. The fergusonite structure is, however, metastable and can only occur if the transition to the P2{sub 1}/n phases were kinetically inhibited. Our experiments in BaWO{sub 4} indicate that it becomes amorphous beyond 47 GPa.