Phase Transformation Driven by Valence Electron Concentration: Tuning Interslab Bond Distances in Gd5GaxGe4-x

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• 作者：Yurij Mozharivskyj ; Wonyoung Choe ; Alexandra O. Pecharsky ; and Gordon J. Miller
• 刊名：Journal of the American Chemical Society
• 出版年：2003
• 出版时间：December 10, 2003
• 年：2003
• 卷：125
• 期：49
• 页码：15183 - 15190
• 全文大小：218K
• 年卷期：v.125,no.49(December 10, 2003)
• ISSN：1520-5126

文摘

X-ray single crystal and powder diffraction studies on the Gd₅Ga_xGe_4-x system with 0 ages/entities/le.gif"> x ages/entities/le.gif"> 2.2reveal dependence of interslab T-T dimer distances and crystal structures themselves on valence electronconcentration (T is a mixture of Ga and Ge atoms). While the Gd₅Ga_xGe_4-x phases with 0 ages/entities/le.gif"> x ages/entities/le.gif"> 0.6 andvalence electron concentration of 30.4-31 e^-/formula crystallize with the Sm₅Ge₄-type structure, in whichall interslab T-T dimers are broken (distances exceeding 3.4 Å), the phases with 1 ages/entities/le.gif"> x ages/entities/le.gif"> 2.2 and valenceelectron concentration of 28.8-30 e-/formula adopt the Pu₅Rh₄- or Gd₅Si₄-type structures with T-T dimersbetween the slabs. An orthorhombic Pu₅Rh₄-type structure, which is intermediate between the Gd₅Si₄- andSm₅Ge₄-type structures, has been identified for the Gd₅GaGe₃ composition. Tight-binding linear-muffin-tin-orbital calculations show that substitution of three-valent Ga by four-valent Ge leads to larger populationof the antibonding states within the dimers and, thus, to dimer stretching and eventually to dimer cleavage.