Abstract
Amorphous Ni–P electrodeposits of various compositions ranging from 16.1 to 25.1 at%P were studied by X-ray diffraction. The interference functions for these alloys are characterized by a shoulder on the high angle side of the second peak. A model for the structure of these alloys was developed. This model, deduced from analysis of the mechanism for the electrodeposition, requires that the alloys consist of distinct basic structural units in the form of triangular clusters, each are composed of two Ni atoms and one P atom, and those excess Ni atoms which control the alloy compositions. The dimensions of the structural units correspond to those of the crystalline compound Ni2P. Model aggregates of various compositions ranging from 20 to 33 at%P have been generated by computer simulation. The principal assumptions involved in generating the aggregates are based on the requirements for electrodeposition. The interference functions calculated from the model aggregates agreed quite well with the diffraction data. These model aggregates have also been used to calculate the radial distribution function, packing density, coordination number, and volume per atom in the bulk structure. The calculated atomic volume for the model is consistent with a recent experimental observation.
