Elementary excitations and crossover phenomenon in liquids

TL;DR

This paper reveals that local configurational excitations, rather than phonons, are the fundamental excitations in high-temperature metallic liquids, explaining complex liquid behaviors like fragility and viscosity increase.

Contribution

It introduces the concept that configurational excitations dominate in liquids and explains the crossover phenomenon through their competition with phonons, supported by molecular dynamics simulations.

Findings

Configurational excitations are the elementary excitations in metallic liquids.

The crossover phenomenon is driven by competition between configurational excitations and phonons.

These excitations help explain liquid fragility and viscosity changes near the glass transition.

Abstract

The elementary excitations of vibration in solids are phonons. But in liquids phonons are extremely short-lived and marginalized. In this letter through classical and ab-initio molecular dynamics simulations of the liquid state of various metallic systems we show that different excitations, the local configurational excitations in the atomic connectivity network, are the elementary excitations in high temperature metallic liquids. We also demonstrate that the competition between the configurational excitations and phonons determines the so-called crossover phenomenon in liquids. These discoveries open the way to the explanation of various complex phenomena in liquids, such as fragility and the rapid increase in viscosity toward the glass transition, in terms of these excitations.