...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Influence of the molecular structures on the high-pressure and low-temperature phase transitions of plastic crystals
【24h】

Influence of the molecular structures on the high-pressure and low-temperature phase transitions of plastic crystals

机译：分子结构对塑料晶体高压和低温相变的影响

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The crystal structures of tert-butyl-tris(trimethylsilyl)silane, Si[C(CH3)(3)](1) [Si(CH3)(3)](3) (Bu1), and di-tert-butyl-bis(trimethylsilyl)silane, Si[C(CH3)(3)](2) [Si(CH3)(3)](2) (Bu2), at room temperature and at 105 K have been determined by X-ray powder diffraction; the high-pressure behavior for pressures between 0 and 5 GPa is reported. The room-temperature structures have cubic Fm (3) over barm symmetry (Z = 4) with a = 13.2645 (2) Angstrom, V = 2333.87 (4) Angstrom(3) for Bu1 and a = 12.9673 (1) Angstrom, V = 2180.46 (3) Angstrom(3) for Bu2. The molecules are arranged in a cubic close packing (c.c.p.) and exhibit at least 48-fold orientational disorder. Upon cooling both compounds undergo a first-order phase transition at temperatures T c = 230 (5) K (Bu1) and Tc = 250 (5) K (Bu2) into monoclinic structures with space group P2(1). The structures at 105 K have a = 17.317 (1), b = 15.598 (1), c = 16.385 (1) Angstrom, gamma = 109.477 (4)degrees, V = 4172.7 (8) Angstrom(3) and Z = 8 for Bu1 and a = 17.0089 (9), b = 15.3159 (8), c = 15.9325 (8) Angstrom, gamma = 110.343 (3)degrees, V = 3891.7 (5) Angstrom(3) and Z = 8 for Bu2. The severe disorder of the room-temperature phase is significantly decreased and only a two- or threefold rotational disorder of the molecules remains at 105 K. First-order phase transitions have been observed at pressures of 0.13-0.28 GPa for Bu1 and 0.20-0.24 GPa for Bu2. The high-pressure structures are isostructural to the low-temperature structures. The pressure dependencies of the unit-cell volumes were fitted with Vinet equations of state and the bulk moduli were obtained. At still higher pressures further anomalies in the pressure dependencies of the lattice parameters were observed. These anomalies are explained as additional disorder-order phase transitions. [References: 29]
机译：叔丁基三（三甲基硅烷基）硅烷，Si [C（CH3）（3）]（1）[Si（CH3）（3）]（3）（Bu1）和二叔丁基-双（三甲基硅烷基）硅烷，Si [C（CH3）（3）]（2）[Si（CH3）（3）]（2）（Bu2）在室温和105 K下通过X射线粉末测定衍射;报告了0至5 GPa之间压力的高压行为。室温结构在barm对称性（Z = 4）上具有立方Fm（3），其中Bu1的a = 13.2645（2）埃，V = 2333.87（4）埃（a）和a = 12.9673（1）埃对于Bu2 = 2180.46（3）埃（3）。这些分子排列成立方紧密堆积（c.c.p.），并表现出至少48倍的取向紊乱。冷却后，两种化合物在温度T c = 230（5）K（Bu1）和Tc = 250（5）K（Bu2）时经历一阶相变，转变为空间群P2（1）/ n的单斜晶结构。在105 K处的结构具有a = 17.317（1），b = 15.598（1），c = 16.385（1）埃，伽马= 109.477（4）度，V = 4172.7（8）埃（3）和Z = 8对于Bu1，a = 17.0089（9），b = 15.3159（8），c = 15.9325（8）埃，伽马= 110.343（3）度，对于Bu2，V = 3891.7（5）埃（3），Z = 8。室温相的严重紊乱得到显着降低，并且分子在105 K时仅保留了两倍或三倍的旋转紊乱。对于Bu1和0.20-0.24，在0.13-0.28 GPa的压力下观察到一级相变。 Bu2的GPa。高压结构与低温结构是同构的。用维涅特状态方程拟合单位晶胞体积的压力依赖性，并获得体积模量。在更高的压力下，观察到晶格参数的压力依赖性进一步异常。这些异常被解释为其他乱序相变。 [参考：29]

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号