Abstract
The local structure of Nisingle bondPd solid solution alloys with compositions of Ni80Pd20 and Ni50Pd50 was investigated with anomalous X-ray diffraction, X-ray absorption and theoretical calculation/simulation. The fcc lattice is distorted for both alloys, and the Pdsingle bondPd atomic pair distance is +4.4% and +1.4% larger than ideal values in Ni80Pd20 and Ni50Pd50 alloys, respectively. The corresponding atomic pair distance of Nisingle bondNi is −1.8% and −3.0% less than the ideal values. Different short-range orders in the alloys were quantitatively identified at the atomic level. In Ni80Pd20, Pd atoms are likely to form Pdsingle bondPd pairs, while Pd atoms are connected with Pd atoms in the second shell in the equiatomic solid solution alloy. Upon ion irradiation, little change of interatomic distance, but modification of chemical short-range order was observed. The number of Pdsingle bondPd pairs decreases to the lowest value at 0.1 dpa, and further irradiation make it increase.