Anamalous-scattering contrast study of the mixed-valence charge-density-wave conductor NbSe3
Anamalous-scattering contrast study of the mixed-valence charge-density-wave conductor NbSe3
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混合价电荷密度波导体NbSe3的反常散射对比研究
DOI：
10.1107/s0108767392011279
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
P. Coppens
中科院分区：
文献类型：
--
作者：
Yan Gao;M. Pressprich;P. Coppens
在混合价固体 NbSe3 的分析中，在 Nb K 边缘采用价态对比衍射法。 NbSe3 结构由三个平行的棱柱配位 Nb 原子链组成，并经历两次低温 Peierls 型相变，从而形成调制结构。先前对同步辐射单晶数据的分析表明，在 145 K 冷却时发生的转变（导致 q1 型调制）涉及 NbIII 原子以及一些配位 Se 原子的位移，而在 59 K 时的第二次转变（q2 型调制）涉及 NbI 原子和 II 列 Se 原子的位移 [van Smaalen、de Boer、Meetsma， Graafsma、Sheu、Darovskikh、Coppens 和 Levy (1992)。物理。修订版 B，45，3103–3106]。目前的室温研究在 Nb 吸收边附近的七个不同波长下进行，结果表明 NbII 原子边沿相对于其他 Nb 原子的边沿向更高能量移动约 5 eV。这表明 NbII 原子导带的数量较少，与能带结构计算一致，但与核磁共振测量得出的结论不一致。
The valence-contrast diffraction method is used at the Nb K edge in the analysis of the mixed-valence solid NbSe3. The NbSe3 structure consists of three parallel chains of prismatically coordinated Nb atoms and undergoes two low-temperature Peierls-type phase transitions that lead to modulated structures. Previous analysis of synchrotron-radiation single-crystal data has shown that the transition that occurs on cooling at 145 K (leading to the q1-type modulation) involves displacements of NbIII atoms as well as of some of the coordinated Se atoms, while the second transition (the q2-type modulation), at 59 K, involves displacements of NbI atoms and an Se atom of column II [van Smaalen, de Boer, Meetsma, Graafsma, Sheu, Darovskikh, Coppens & Levy (1992). Phys. Rev. B, 45, 3103–3106]. The present room-temperature study, performed at seven different wavelengths in the vicinity of the Nb absorption edge, shows the NbII-atom edge to be shifted to higher energies by about 5 eV relative to those of the other Nb atoms. This indicates a smaller population of the NbII-atom conduction band, in agreement with band structure calculations but not with conclusions derived from nuclear magnetic resonance measurements.