Radial distribution function and structural relaxation in amorphous solids

Abstract

A method of interpreting radial distribution functions (RDF) of amorphous metals is proposed in which the role of the local atomic structure is emphasized. It is found that the width and height of the peaks of the RDF are related to the second moment of the atomic-level hydrostatic stress distribution $〈p^2〉$. The results of this analysis are then used to explain the details of the changes that occur in the RDF when structural relaxation takes place. The theoretical ▵RDF is found to be in excellent agreement with the results of a computer study and previous experimental results. It is further proposed that changes in $〈p^2〉$ may be most easily accounted for in terms of changes in the density of the structural defects defined in terms of the local fluctuations in the hydrostatic stress. In this way the changes that occur in the structure of amorphous metal during structural relaxation, as represented by the RDF, may be explained in terms of the motion and annihilation of these structural defects. It is concluded that the number density of defects which could account for the observed changes in the experimental RDF is 10%. It is also found that while the hydrostatic stress distribution may be significantly changed during structural relaxation, the distribution of the atomic-level shear stresses remains unaltered.