Structural Relaxation Of Nanoglass And Its Correlation With Potential Energy Landscape

Glass has always been an important research object in condensed matter physics.At present,the core difficulty in the dynamic research on glass is that during the glass transition process,the structure of the system hardly changes,but the structure relaxation time increases exponentially with the decrease of temperature,which leads to the extremely slow dynamic processes at low temperature.In this article,we use molecular dynamics simulation to study the structural relaxation behavior of nanoglass and its possible correlation or correspondence with the potential energy landscape.The main results are summarized as follows:1.Fragility crossover also exists in monometallic nanoglass,i.e.,at the crossover temperature,the fragility of the system shows a fragile-strong crossover.This phenomenon is widespread in polymer and alloy glasses.2.The fragility of glass is closely related to the distribution of barrier heights on potential energy landscape.The barrier heights of strong glass are mainly distributed in a small interval,while the barrier heights of fragile glass vary in a wider range.When adjusting the barrier heights,the fragility of the system changes correspondingly.We have found that the temperature dependence of structural relaxation time of glasses with different fragility can be described by a unified scaling law.3.After the fragility crossover occurs,the potential energy of system obeys a nonGaussian distribution,while the system presents significant temporal dynamic heterogeneity.By studying the short-term average of potential energy,we have found that these behaviors are determined by the characteristic structure of the potential energy landscape: below the crossover temperature,the depths of basins are distributed over a series of energy levels,and the difference between adjacent levels barely varies with temperature change.Such characteristic structures are common in different systems.