Mean-field model of melting in superheated crystals based on a single experimentally measurable order parameter

Abstract

Melting is one of the most studied phase transitions important for atomic, molecular, colloidal, and protein systems. However, there is currently no microscopic experimentally accessible criteria that can be used to reliably track a system evolution across the transition, while providing insights into melting nucleation and melting front evolution. To address this, we developed a theoretical mean-field framework with the normalised mean-square displacement between particles in neighbouring Voronoi cells serving as the local order parameter, measurable experimentally. We tested the framework in a number of colloidal and in silico particle-resolved experiments against systems with significantly different (Brownian and Newtonian) dynamic regimes and found that it provides excellent description of system evolution across melting point. This new approach suggests a broad scope for application in diverse areas of science from materials through to biology and beyond. Consequently, the results of this work provide a new guidance for nucleation theory of melting and are of broad interest in condensed matter, chemical physics, physical chemistry, materials science, and soft matter.

Surface Premelting and Melting of Colloidal Glasses

“…3h). These behaviours agree with the predictions in Landau theory 33 and observations in crystal melting experiment 9 . The constant speed of melting front has also been observed in ultrastable glass melting 4,14 , whereas the constant width of the melting front has only been conjectured in ultrastable glass without an experimental test 5 .…”

“…Behaviours (2 and 4) hold for melting under the fast temperature change. Behaviours (1, 2 and 4) have been experimentally observed in crystal premelting 29,36 and melting 9 , whereas the theoretical prediction of behaviour (3) 28 has not been tested in crystals due to the lack of single-particle resolution. Melting is always easier from a free surface than within bulk for ordinary and ultrastable glasses (Supplementary Information E), but glass surface premelting has not been discussed and glass surface melting lacks theory.…”

Surface premelting and melting of colloidal glasses

“…The hyperbolic tangent profile commonly exists on vapor-liquid interfaces ( 47 ), liquid-solid interfaces ( 48 , 49 ), vapor-solid interfaces ( 50 ), and solid-solid interfaces ( 51 ). In addition, error function (erf), the prediction of Landau theory for crystal premelting ( 45 ), and the Fisk-Widom (FW) function for the interface between fluid phases can fit normalρfalse~false(yfalse).1emand.1emsfalse~2false(yfalse) equally well (Fig.…”

The role of attraction in the phase diagrams and melting scenarios of generalized 2D Lennard-Jones systems

“…87 . The method allows obtaining a binodal in the coordinates density-temperature using analysis of Voronoi cells in the system and, in particular, in terms of the following order parameter 59,87 :…”

“…The role of attraction can be tested experimentally in colloidal systems, known for a long time as model systems demonstrating a wide range of "molecularlike" phenomena 1,[47][48][49][50] , in particular, crystallization and melting [51][52][53][54][55][56][57][58][59] , solid-solid phase transitions [60][61][62] , condensation and critical phenomena [63][64][65] caused by relatively short-range attractive depletion forces 66 . These collective phenomena can be visualized in real-time with spatial resolution of individual particles.…”