Tuktabiev M A, Popova S V, Brazhkin V V, Lyapin A G, Katayama Y
Institute for High Pressure Physics, Russian Academy of Sciences, 142190, Troitsk, Moscow region, Russia.
J Phys Condens Matter. 2009 Sep 23;21(38):385401. doi: 10.1088/0953-8984/21/38/385401. Epub 2009 Aug 24.
The energy-dispersive x-ray diffraction technique has been employed to study the structure and equation of state of realgar As(4)S(4) under pressures up to 8 GPa at room temperature. We have obtained pressure dependences of the unit cell parameters and volume for the monoclinic structure of realgar. An approximation of the equation of state through the Murnaghan equation gives the bulk modulus and its derivative, B(0) = 8.1 ± 0.5 GPa and B(0)(') = 9.0 ± 0.5, respectively. A comparison of the obtained values with the corresponding values for other molecular crystals is drawn and discussed. At a pressure of around 7 GPa, realgar showed a polymorph transition to a new molecular phase with a supposedly orthorhombic structure. Such identification is evidenced by the presence of geometrical correlations between the parameters of the parent monoclinic phase and those of the new phase, and the phase transition is likely to be associated with the removal of a monoclinic distortion in the unit cell.
利用能量色散X射线衍射技术研究了室温下压力高达8吉帕时雄黄As(4)S(4)的结构和状态方程。我们获得了雄黄单斜结构的晶胞参数和体积随压力的变化关系。通过莫纳汉方程对状态方程进行近似，得到了体模量及其导数，分别为B(0)=8.1±0.5吉帕和B(0)'=9.0±0.5。对所得值与其他分子晶体的相应值进行了比较和讨论。在约7吉帕的压力下，雄黄显示出向一种新的分子相的多晶型转变，该新相可能具有正交结构。母体单斜相和新相参数之间存在几何相关性，这证明了这种识别，并且相变可能与晶胞中单斜畸变的消除有关。
