S.N. Ishmaev

Direct evidence for B-B contact in amorphous Ni2B from high-resolution neutron diffraction

The short range structure in amorphous Ni 2 B has been investigated by high spatial resolution neutron diffraction. Three specimens of the same chemical composition but with different isotopic content of nickel, nat Ni, 60 Ni and φ Ni, were examined. The B-B, B-Ni and Ni-Ni atomic pair correlation and the Bhatia-Thornton density-concentration correlation functions were derived with high accuracy. The first neighbour atomic distances, the width of their distribution and the coordination numbers are given. The existence of first neighbour B-B distance at 0.187 nm is established. The distribution width in the first coordination shell for unlike atoms was found to be significantly smaller than that for similar type atom pairs.

Short range order in amorphous in Ni62Nb38studied by isotopic neutron diffraction

Abstract The short range structure of amorphous Ni 62 Nb 38 has been investigated by high spatial resolution neutron diffraction. Four specimens of the same chemical composition but with different isotopic content of nickee were examined. The three partial atomic structure factors as well as the density-concentration structure factors were evaluated, and the corresponding pair correlation functions derived. The results indicate that this metal-metal type amorphous alloy is not a substitutional one and preferential correlation exists between unlike atoms.

Partial correlations in NiNb amorphous alloys

Short range order in amorphous Ni 44 Nb 56 was investigated using time-of-flight neutron diffraction. The total structure factors were measured for three isotope substituted Ni 44 Nb 56 samples with 58 Ni, 60 Ni, and 0 Ni (a mixture of 62 Ni and 60 Ni isotopes with zero average coherent scattering amplitude). The partial structure factors, the atomic and the density-concentration correlation functions were determined. The characteristic parameters of the short range order are given, i.e., the neighbouring atomic pair distances, their distribution width and the coordination numbers. The results are compared with those given in the literature for amorphous Ni 62 Nb 38 , and the concentration dependence is analyzed in the amorphous Ni Nb system. It is established that chemical short range order is stronger in Ni-rich samples.

Generation of Ni44Nb56 and Ni62Nb38 metallic glass computer models and investigation of their structures

Abstract Computer models of Ni44Nb56 and Ni62Nb38 metallic glasses were generated using the original iterative procedure based on the molecular dynamics method and the Born-Green-Bogoljubov equation (without use of the superposition approximation). Analysis of the first neighbor shells, large cavities and Voronoy polyhedra distributions was performed. It was found that the structure of the Ni44Nb56 metallic glass is less ordered and less dense than the structure of the Ni62Nb38 metallic glass.

Computer simulation of a Ni65B35 amorphous alloy using the force algorithm

Abstract A Ni 65 B 35 amorphous alloy model (1000 particles in a basic cube) has been generated using neutron structure data and a force algorithm. The direct contact between boron atoms at a distance of 0.187 nm is found in agreement with experiment. The structure of the model is analyzed and it is concluded that the -B-B-B- linear chains are destroyed on the amorphization of crystalline Ni 2 B.

Short range order in amorphous Zn41Sb59 obtained by thermopressure processing

Abstract The short range order of amorphous Zn 41 Sb 59 obtained by spontaneous amorphization of the metastable metallic high-pressure phase has been investigated. The structure factor was determined by time-of-flight neutron diffraction on the pulsed neutron source of LINAC ‘Fakel’ in the range of momentum transfer up to 17 A −1 and the radial distribution function was calculated. It is shown that the structure of the amorphous phase is similar to that of the crystalline semiconductor phase ZnSb.