Anomalous x-ray scattering measurement of near-neighbor individual pair displacements and chemical order inFe22.5Ni77.5

We demonstrate an anomalous x-ray-diffraction procedure for the determination of pair correlations in crystalline solid solutions. This procedure experimentally removes the large thermal diffuse scattering background with no assumptions and permits separation of chemically specific static displacements. We recover the near-neighbor chemical order and static displacements in a ${\mathrm{Fe}}_{22.5}$ ${\mathrm{Ni}}_{77.5}$ single crystal quenched from 1000 °C. The Fe-Fe nearest-neighbor distance is dilated by ∼0.043 Å from the average lattice. The possible magnetic origins of this dilation are discussed.