Menushenkov A P, Klementev K V, Cortes R, Purans J
Moscow State Engineering Physics Institute, Russia.
J Synchrotron Radiat. 2001 Mar 1;8(Pt 2):845-7. doi: 10.1107/s0909049501000115.
Temperature dependent x-ray absorption spectra investigation were measured for Ba(1-x)K(x)BiO3 (Bi L3-edge) with x =0.0, 0.25, 0.4, 0.5 and for BaPbO3 (Pb L3-edge). It was found that at low temperatures the Debye-Waller factor of the square diagonal Bi-Bi bond has the maximum value near the insulator-metal phase transition for the compound with x = 0.25 and x = 0.4. Temperature dependence of the Debye-Waller factor of Bi-Bi bond strongly differs from the Einstein model curve that well describes the harmonic systems (for example BaPbO3). This behavior is consistent with the strong anharmonicity of the Bi-O shell due to the double-well vibration potential reported by us earlier. Presented results point to the essential lattice softening of the superconducting compositions, which is important for the understanding of superconductivity mechanism in perovskite type oxides.
对x = 0.0、0.25、0.4、0.5的Ba(1-x)K(x)BiO3（Bi L3边）以及BaPbO3（Pb L3边）进行了温度相关的x射线吸收光谱研究。研究发现，在低温下，对于x = 0.25和x = 0.4的化合物，方形对角Bi-Bi键的德拜-瓦勒因子在绝缘体-金属相变附近具有最大值。Bi-Bi键的德拜-瓦勒因子的温度依赖性与能很好描述谐波系统（例如BaPbO3）的爱因斯坦模型曲线有很大不同。这种行为与我们之前报道的由于双阱振动势导致的Bi-O壳层的强非谐性一致。给出的结果表明超导组合物的晶格有本质软化，这对于理解钙钛矿型氧化物中的超导机制很重要。
