ABINITIO CURVED-WAVE X-RAY-ABSORPTION FINE-STRUCTURE
ABINITIO CURVED-WAVE X-RAY-ABSORPTION FINE-STRUCTURE
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DOI：
10.1103/physrevb.44.4146
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发表时间：
1991-09-01
影响因子：
3.7
通讯作者：
ALBERS, RC
中科院分区：
文献类型：
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作者：
DELEON, JM;REHR, JJ;ALBERS, RC
研究了X射线吸收精细结构（XAFS）从头算计算中最重要的元素。为了获得准确的结果，没有特设的可调参数，我们发现它必须包括（i）弯曲波效应，（ii）一个复杂的，依赖于能量的自能，（iii）一个近似的分子势，和（iv）一个固定的能量参考光电子波数。基于这些发现，一个自动化的代码已开发的从头计算单散射XAFS，其中弯曲波的影响被视为正是在有效的背散射振幅，非弹性损失和自能位移被纳入使用的Hedin-Lundqvist自能，一个自动相对论性的双原子松饼锡势，和能量阈值估计从电子气体理论。代码的效率是可能的Hedin-Lundqvist自能的解析表达式。该代码取代了现有的XAFS相位和散射振幅表，并为整个周期表中的任意原子对（Z小于或等于94）产生可靠的理论XAFS标准。这些结果与自洽计算的结果相当，并且在吸收边的约20 eV内有效。与实验的比较Cu，Ge，Pt，Br 2，和GeCl 4。计算出的XAFS振幅被认为是准确的15%以内; XAFS相位是准确的0.2弧度内;最近邻距离通常是准确的0.02埃内。
The most important elements of ab initio calculations of x-ray-absorption fine structure (XAFS) are studied. To obtain accurate results without ad hoc adjustable parameters, we find it essential to include (i) curved-wave effects, (ii) a complex, energy-dependent self-energy, (iii) an approximate molecular potential, and (iv) a fixed energy reference for the photoelectron wave number. Based on these findings, an automated code has been developed for ab initio calculations of single-scattering XAFS, in which curved-wave effects are treated exactly in terms of effective backscattering amplitudes, inelastic losses and self-energy shifts are incorporated with use of a Hedin-Lundqvist self-energy, an automated relativistic overlapping-atom muffin-tin potential is used, and the energy threshold is estimated from electron-gas theory. The efficiency of the code is made possible by analytic expressions for the Hedin-Lundqvist self-energy. This code replaces existing tables of XAFS phases and scattering amplitudes and yields reliable theoretical XAFS standards for arbitrary pairs of atoms throughout the Periodic Table (Z less-than-or-equal-to 94). These results are comparable to those from self-consistent calculations and are valid to within about 20 eV of the absorption edge. Comparisons with experiment are presented for Cu, Ge, Pt, Br2, and GeCl4. The calculated XAFS amplitudes are found to be accurate to within 15%; XAFS phases are accurate to within 0.2 rad; and nearest-neighbor distances are typically accurate to within 0.02 angstrom.