Computer Simulation of Amorphous Ni–Nb Alloys from Diffraction Data

Force constant disorder in the Ni44Nb56 bulk metallic glass as observed by deep inelastic neutron scattering augmented by isotopic substitution

“…Interestingly, the ratio of the force constant of nickel to that of niobium, obtained in this work (0.82), agrees very well with the value reported in the neutron inelastic scattering study of Ni 44 Nb 56 [43] and calculated from the second moments of the apVDOSs of nickel and niobium extracted from measured inelastic neutron scattering spectra [43]. Moreover, the results of structure and dynamics simulations using the reverse Monte Carlo approach augmented with an effective force field yielded a value of 0.74 [111]. Interestingly, the value of 0.82 is obtained instead of 0.74 using equation 3 and the NMD width values obtained from apVDOSs of nickel and niobium taken from the same work, instead of the calculation using the second moments of the apVDOSs [111].…”

“…The mean values of the effective force constants obtained from DINS experiments in Ni 44 Nb 56 compare favourably with the values reported in the literature for other glassy systems and parent compounds (e.g. metal oxides) used for glass synthesis [43,[103][104][105][106][107][108][109][110][111]. They yield 0.75 eV Å 2, and 0.91 eV Å 2 in the case of nickel and niobium, respectively, and are equal to the average force constant values, calculated based on the ab initio HLD simulations for crystals of nickel, niobium and NiNb.…”

“…In the case of Ni 44 Nb 56 , the theoretical analysis of neutron diffraction data reveals peaks at 2.61 Å, 2.91 Å, and 2.97 Å, for the Ni-Nb, Nb-Nb, and Ni-Ni partial reduced radial distribution functions, respectively [114]. A similar analysis performed by Svab et al [41] [120], the mean interatomic distances and coordination numbers in Ni 44 Nb 56 slightly depend on the simulation algorithm adopted to analyse the data. To this end, the authors compared four different algorithms: (i) reverse Monte Carlo (RMC), (ii) Schommers, (iii) Mendelev-Belashchenko (MB), and (iv) a classical force-field augmented RMC computational scheme referred to as the hybridisation algorithm.…”

“…Moreover, the results of structure and dynamics simulations using the reverse Monte Carlo approach augmented with an effective force field yielded a value of 0.74 [111]. Interestingly, the value of 0.82 is obtained instead of 0.74 using equation 3 and the NMD width values obtained from apVDOSs of nickel and niobium taken from the same work, instead of the calculation using the second moments of the apVDOSs [111]. However, it should be noted that using the same values of reduced masses (equal to the average atomic weights of nickel and niobium) for all vibrational modes present in apVDOSs causes systematic errors in the calculation of NMD widths.…”

COLLABORATIVE RESEARCH AND DEVELOPMENT (CR&D) Task Order 0039: Topologically Constrained Networks in Metallic Glasses

“…For the Ni-Nb system, the composition range for X* corresponds to 0.43 ± 0.07 (i.e., 0.36 to 0.50). The actual data [6,7] in the Ni-Nb system show that good glass formation occurs at several compositions 0.37,0,44,0.50, and 0.60. The first three are all within the predicted range.…”