Ultrahigh Poisson's ratio glasses

The manner in which metallic glasses fail under external loading is known to correlate well with those glasses' Poisson's ratio ν: Low-ν (compressible) glasses typically feature brittle failure patterns with scarce plastic deformation, while high-ν (incompressible) glasses typically fail in a ductile manner, accompanied by a high degree of plastic deformation and extensive liquidlike flow. Since the technological utility of metallic glasses depends on their ductility, materials scientists have been concerned with fabricating high-ν glassy alloys. To shed light on the underlying micromechanical origin of high-ν metallic glasses, we employ computer simulations of a simple glass-forming model with a single tunable parameter that controls the interparticle potential's stiffness. We show that the presented model gives rise to ultrahigh-ν glasses, reaching ν = 0.45 and thus exceeding the most incompressible laboratory metallic glass. We discuss the possible role of the so-called unjamming transition in controlling the elasticity of ultrahigh-ν glasses. To this aim, we show that our higher-ν computer glasses host relatively softer quasilocalized glassy excitations, and establish relations between their associated characteristic frequency, macroscopic elasticity, and mechanical disorder.