Radial Distribution Function and Structural Relaxation in Amorphous Solids

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 ⟨p2⟩. 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 ⟨p2⟩ 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. Disciplines Atomic, Molecular and Optical Physics | Engineering | Materials Science and Engineering | Metallurgy | Structural Materials This journal article is available at ScholarlyCommons: http://repository.upenn.edu/mse_papers/238 PHYSICAL REVIEW B VOLUME 24, NUMBER 12 15 DECEMBER 1981 Radial distribution function and structural relaxation in amorphous solids D. Srolovitz, T. Egami, and V. Vitek Department of Materials Science and Engineering and Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (Received 13 April 1981; revised manuscript received 14 August 1981) 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'). 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 hRDF 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 ) tnay 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.