Lattice distortion of solute atoms in metals studied by x-ray-absorption fine structure

The analysis of the x-ray-absorption fine structure (XAFS) yields information about the local atomic arrangement of the absorbing atom. The technique was used to study systematically the lattice dilatation or compression caused by substitutional impurity atoms in the fcc metals Al, Cu, Ni, Pd, and Ag and the bcc metals Fe, Nb, and V. Measuring XAFS spectra at the K and L edges of a variety of metals, interatomic distances, coordination numbers, and Debye-Waller factors were determined. Using experimentally determined amplitudes and phases from appropriate model compounds, the accuracy of the analysis is about 0.5% for nearest-neighbor distances and about 10% for coordination numbers and Debye-Waller factors. For the 61 systems investigated, shifts of the first-neighbor-shell distance of up to 10 pm are found, while the shifts of higher shells are generally small. Systematic variations within the rows of the Periodic Table are observed, indicating the importance of electronic effects. The results are discussed in comparison with lattice-parameter measurements and band-structure calculations.