Duality of liquids

TL;DR

This paper presents a new perspective on liquids, showing they exhibit a duality by being thermodynamically similar to solids yet flowing like gases, based on vibrational and diffusional motion analysis.

Contribution

It introduces a novel approach focusing on vibrational versus diffusional contributions, revealing liquids' dual nature from thermodynamic and flow perspectives.

Findings

Liquid energy and specific heat are mainly vibrational, similar to solids.

Liquids exhibit a duality: solid-like thermodynamics and gas-like flow.

The approach spans relaxation times over 15 orders of magnitude.

Abstract

Liquids flow, making them remarkably distinct from solids and close to gases. At the same time, interactions in liquids are strong as in solids. The combination of these two properties is believed to be the ultimate obstacle to constructing a general theory of liquids. Here, we adopt a new approach to liquids: instead of focusing on the problem of strong interactions, we zero in on the relative contributions of vibrational and diffusional motion in liquids. We subsequently show that from the point of view of thermodynamics, liquid energy and specific heat are given, to a very good approximation, by their vibrational contributions as in solids, for relaxation times spanning 15 orders of magnitude. We therefore find that liquids show an interesting {\it duality} not hitherto known: they are close to solids from the thermodynamical point of view and to gases from the point of view of flow. We discuss the experimental implications of this approach.