TEMPERATURE-DEPENDENCE OF THE STRUCTURE FACTOR IN NB-NI GLASSES

Using the results of x-ray scattering experiments, the structure factor S(k), the radial distribution function, and the coordination number have been determined at room temperature for two Nb-Ni glass samples (of composition Nb0.4Ni0.6 and Nb0.5Ni0.5). Furthermore, the height of the first peak in the structure factor, S(kp), has been measured as a function of temperature for these two samples in the range 4-675 K. S(kp) remains approximately constant from 4 to 100 K, after which it decreases linearly with increasing temperature until the glass crystallizes at 675 K. This behavior is in excellent agreement with a recent calculation which expresses the temperature dependence of S(k) of an amorphous metal in terms of the Debye-Waller factor. According to the Ziman theory for the resistivity of amorphous metals, a decrease of S(kp) with increasing temperature may lead to a negative temperature coefficient of resistivity as has been observed in these glasses. The observed change of S(kp) is large enough to account for the observed change in resistivity at room temperature and above. Possible reasons for the discrepancy between the Ziman theory and the structure-factor data below room temperature are discussed. © 1979 The American Physical Society.