Department of Chemical Engineering and Materials Science, University of California Davis, Davis, California 95616, USA.
J Phys Chem B. 2011 Mar 31;115(12):2857-63. doi: 10.1021/jp111641f. Epub 2011 Mar 9.
The structure of phosphorus selenide glasses with compositions close to the P(4)Se(3) stoichiometry with and without doping with a few atom % Ge has been investigated with Raman and (31)P NMR spectroscopic techniques. The results indicate that the structure of these glasses consists predominantly of P(4)Se(3) cage molecules. However, in spite of this structural similarity, doping with Ge results in a remarkably large increase in T(g). The dynamical behavior of the constituent P(4)Se(3) molecules in the Ge-free composition is investigated with a (31)P NMR hole-burning technique in the supercooled liquid state. These molecules perform large angle rotational reorientations near and above the glass transition with time scales similar to those expected for shear relaxation. Such coupling between molecular rotation and shear relaxation processes near T(g) is reminiscent of the dynamical behavior of organic molecular glass-forming liquids. However, this behavior is in stark contrast with the large temporal decoupling between molecular rotation and shear relaxation previously reported for a Ge-doped arsenic sulfide liquid that contained similarly structured As(4)S(3) cage molecules.
用拉曼和 (31)P NMR 光谱技术研究了组成接近 P(4)Se(3)化学计量比的磷硒化物玻璃以及掺杂少量原子%Ge 的磷硒化物玻璃的结构。结果表明，这些玻璃的结构主要由 P(4)Se(3)笼状分子组成。然而，尽管结构相似，但掺杂 Ge 会导致 T(g)显著增加。用 (31)P NMR 孔烧蚀技术在过冷液体状态下研究了无 Ge 组成中 P(4)Se(3)分子的动力学行为。这些分子在玻璃化转变附近和上方进行大角度旋转重取向，时间尺度与剪切松弛预期的时间尺度相似。这种分子旋转和剪切松弛过程之间的耦合在 T(g)附近类似于有机分子玻璃形成液体的动力学行为。然而，这种行为与之前报道的掺 Ge 的砷硫化物液体中分子旋转和剪切松弛之间的大时间解耦形成鲜明对比，该液体含有类似结构的 As(4)S(3)笼状分子。
