用微扰角关联法测定In70-Ni30和In70-Pd30的晶体结构
Determination of the crystal structures of In70-Ni30 and In70-Pd30 using perturbed angular correlation
摘要：
根据基于X射线测量的相图，In 70-Pt 30具有立方Sn 7Ir 3晶体结构（D8 f，cI 40），但是合金In 70-Ni 30和In 70-Pd 30已经被各种报道为具有立方γ-黄铜（D81-3，cI 52）或Sn 7Ir 3结构。在这项研究中，超精细相互作用测量作为一种替代方法来识别相位。扰动角相关（PAC）测量的特征核四极相互作用的111 In/Cd探针原子，并证明了一个共同的，特征性的“签名”的Sn 7Ir 3结构在所有三种合金。Sn 7Ir 3结构具有两个不等价的Sn-位点，原子比为3：4，并且点对称性表明两个位点处的电场梯度应该是轴对称的。所有三种合金的测得的扰动函数表现出两个轴对称的四极相互作用信号，具有预期的3：4的振幅比，如预期的结构。此外，每种合金中两个四极相互作用频率的比率都很大，In（3）位点上的探针原子频率大约是In（4）位点上的五倍。综上所述，这些观察结果证实了所有三相都具有Sn 7Ir 3结构。四极相互作用频率也报告了镓与Pt，Pd和Ni的同构合金。可忽略不计的不均匀加宽，观察到在室温附近的所有六个阶段的测量，表明在化学计量比70：30的组合物优良的原子有序。
英文摘要：
According to phase diagrams based on x-ray measurements, In70-Pt30 has the cubic Sn7Ir3 crystal structure (D8f, cI40) but the alloys In70-Ni30 and In70-Pd30 have been variously reported to have either a cubic gamma-brass (D81-3, cI52) or the Sn7Ir3 structures. In this study, hyperfine interaction measurements are applied as an alternate method to identify phases. Perturbed angular correlation (PAC) measurements were made of characteristic nuclear quadrupole interactions of 111In/Cd probe atoms, and demonstrated a common, characteristic "signature" of the Sn7Ir3 structure in all three alloys. The Sn7Ir3 structure has two inequivalent Sn-sites with a 3:4 ratio of atoms and point symmetries indicate that the electric-field gradients at both sites should be axially symmetric. Measured perturbation functions for all three alloys exhibited two axially symmetric quadrupole interaction signals having the expected 3:4 ratio of amplitudes, as expected for the structure. Furthermore, ratios of the two quadrupole interaction frequencies in each alloy were characteristically large, with frequencies for probe atoms on In(3) sites roughly five times greater than on In(4) sites. Taken together, these observations confirm that all three phases have the Sn7Ir3 structure. Quadrupole interaction frequencies are also reported for isostructural alloys of gallium with Pt, Pd and Ni. Negligible inhomogeneous broadening was observed in measurements near room temperature in all six phases, indicating excellent atomic ordering at the stoichiometric 70:30 compositions.
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