EXAFS and XPS Study of Rutile‐Type Difluorides of First‐Row Transition Metals
EXAFS and XPS Study of Rutile‐Type Difluorides of First‐Row Transition Metals
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DOI：
10.1063/1.2644559
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发表时间：
2007-02
期刊：
影响因子：
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通讯作者：
K. Murai;Yohei Suzuki;T. Moriga;A. Yoshiasa
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文献类型：
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作者：
K. Murai;Yohei Suzuki;T. Moriga;A. Yoshiasa
虽然大多数金红石型二氟化物（MnF 2、CoF 2和NiF 2）具有正的热膨胀系数，但FeF 2在高温区域沿c轴沿着具有负的热膨胀（NTE）。在这项研究中，我们用扩展X射线吸收精细结构（EXAFS）和X射线光电子能谱（XPS）技术解释了这种行为。从EXAFS结果可以看出，在高温区域，FeF 6八面体的共享边（Fe-Fe）的长度随着温度的升高而增加。我们发现，在FeF 2中，最近邻原子之间的力常数（Fe-F）远大于次近邻原子之间的力常数（Fe-Fe）。在XPS测量中，发现与其它二氟化物相比，FeF 2的F1 s峰位于最低结合能位置。这意味着FeF 2中F原子周围的电荷密度高于其他二氟化物。由此得出结论，FeF 2中的共享边缘排斥力大于其他二氟化物。由于最近邻原子之间的排斥力和力常数很大，随着温度的升高，Fe原子被吸引到共享边缘。
Although most rutile‐type difluorides (MnF2, CoF2 and NiF2) have a positive thermal expansion coefficient, FeF2 has a negative thermal expansion (NTE) along the c‐axis in the high temperature region. In this study, we give an explanation of that behavior with Extended X‐ray Absorption Fine Structure (EXAFS) and X‐ray Photoelectron Spectroscopy (XPS) techniques. From EXAFS results, it has become apparent that the length of the share‐edge (Fe‐Fe) of FeF6 octahedra increased with the rise of temperature in the high temperature region. We have revealed that the force constant between nearest neighbor atoms (Fe‐F) was much larger than that between second‐nearest neighbor atoms (Fe‐Fe) in FeF2. In XPS measurements, it was discovered that the peak of F 1s of FeF2 was located at the lowest binding energy position as compared to that of other difluorides. This means that the charge density around the F atom in FeF2 was higher than that in other difluorides. It follows from this that the share‐edge repulsive force in FeF2 is larger than that in other difluorides. On account of the large repulsive force and the large force constant between nearest neighbor atoms, Fe atoms are attracted to share‐edge with the rise of temperature.