Short-range order in structural models of metallic glass alloys containing Ti

Considerable effort has gone into determining order at an atomically local scale in metallic glass alloys. For those alloys which contain approximately 20% metalloid, the lack of metalloid-metalloid near neighbor pairs has been confirmed and this fact fits intuitive expectations. Recent evidence has been accumulating that similar kinds of order also exist in glasses containing no metalloid elements; e.g. Ti-Cu and Ti-Ni. In these cases the suggestion from neutron diffraction data is that Cu-Cu (or Ni-Ni) near-neighbor pairs occur less frequently than one would expect from a random distribution. On the other hand the measurements on Zr-Cu glasses do not seem to indicate the same kind of order as deduced from the Ti-Cu measurements. The present paper attempts to unravel some of the facts by studying computer simulated models of the atomic structure of such alloys. Detailed analyses are presented in terms of the concentration-concentration correlation statistical distribution functions. The shape of the distributions are affected by various controls on the short-range order of the models. The theoretical efforts attempt to establish the proper conclusions that may be drawn from experimental probes.