Atomic Structure of Amorphous Metallic Ni₈₁B₁₉

Abstract

The three partial Faber Ziman structure factors as well as the Bhatia Thornton structure factors of the metallic glass NigiBig were evaluated by neutron diffraction experiments using the isotopic substitution method. In one of the investigated specimens the isotopic composition of the components was adjusted in such a way as to make it possible to measure directly with one diffraction experiment the correlation between the metalloid atoms. From the three partial pair correlation functions the atomic distances and the partial coordination numbers are determined. The results demonstrate the strong chemical ordering in amorphous NisiBig. Particularly the distance correlation between the boron atoms turned out to be very pronounced.The experimental results agree with the main features of a geometrical packing model of soft spheres.

Neutron Diffraction Study on the Structure of the Metallic Glass Cu57Zr43

“…With the R t j, Z, 7 , and the widths a^ of the five distributions given in [15] a total G(R) corresponding to Cu6oZr4o was simulated as sum of five Gaussian curves using the appropriate weighting factors. Mathematical details are described in previous papers [84,95], Figure 6 a (dash dotted curve) shows the result, and one can see that the agreement is poor.…”

“…It may be noted that this asymmetric structural behaviour is found to be much more rigorous in metallic glasses of the metal-metalloid type. In this type of glasses direct neighbourhood between the smaller metalloid atoms is avoided and thus the partial metalliod-metalloid structure factor shows a peak at lower (2-values than the main peak of the total X-ray structure factor [84], It is therefore suggested that this asymmetric behaviour, more or less pronounced, is a common feature of all types of metallic glasses.…”

“…The counting statistic per measured point corresponded to 0.5 pet statistical error. The necessary corrections for the evaluation of the coherent intensity from the measured data were essentially the same as described earlier [84], Smoothing of the measured curves was performed with a cubic spline fit procedure. For the macroscopic density the value 7.51 g/cm 3 was taken [85].…”

A Physical Model for Metallic Glass Structures: An Introduction and Update

“…Medium-range order (MRO) in amorphous metals was first seen 30 years ago, 8 but its physical origin and the specific type of order remained unknown for many years. The ECP model gave the first physical description for the origin of this MRO, and also suggests a particular type of order that can be checked directly with experiment.…”

“…Amorphous metals were shown to have significant shortrange atomic order, 7 and since 1982 a surprising degree of medium-range order has been measured. 8 The origin of this order, and its description, also remained a mystery for many years.…”