Correlated disorder in a model binary glass through a local SU(2) bonding topology

Abstract

A quantitative understanding of the microscopic constraints, which underlie a well relaxed glassy structure, is the key to developing a microscopic theory of structural evolution and plasticity for the amorphous metallic solid. Here we demonstrate the applicability of one such theory of local bonding constraints developed by D. R. Nelson [Phys. Rev. B 28, 5515 (1983)PRBMDO0163-182910.1103/PhysRevB.28.5515] for a model binary Lennard-Jones glass structure. By introducing a modified radical Voronoi tessellation, which removes some ambiguity in how nearest-neighbor bonds are enumerated, it is found, that a large proportion (>95%) of local atomic environments follow the connectivity rules of the SU(2) topology resulting in a dense network of disclination lines characterizing the defect bonds. Furthermore, it is numerically shown that a low-energy glass structure corresponds to a reduced level of bond-length frustration and thus a minimally defected bond-defect network. It is then demonstrated that such a defect network provides a framework to analyze thermally activated structural excitations, revealing those high-energy/low-density/elastically soft regions not following the connectivity constraints are more likely to undergo structural rearrangement that often ends with the creation of new SU(2) local topology content. The work provides a new analysis tool to study the connectivity of developing structural motives characteristic of isotropic undercooled liquids, their transition to a glass, and subsequent glassy structural relaxation.