Wall-induced phase transition controlled by layering freezing

Abstract

Molecular dynamics simulations of the Lennard-Jones model are used to study phase transitions at a smooth surface. Our motivation is the observation that the existence of an attractive wall facilitates crystallization. To investigate how this wall influences phase transitions, the strength of wall-particle interaction is varied in our studies. We find that the phase behavior depends on the strength parameter α, i.e., the ratio between wall-particle and the particle-particle attraction strength. Three critical values of the ratio, namely, αp, αw, and αc, are used to define the qualitative nature of the phase behaviors at a smooth surface. Some interesting phenomena due to the increase of α are observed. First, a set of close-packed planes, i.e., {111} planes in fcc structures or {0001} planes in hcp structures, are "rotated" from intersecting to parallel to the wall when α = αp; second, the layering phase transition close to the wall antecedes that of the bulk when α = αw. Finally, the first-order phase transition in the first two layers is supplanted by a continuous phase transition when α = αc, which to some extent can be treated as a quasi-two-dimensional process. We find that bulk freezing always discontinuously occurs through a first-order phase transition, and seems to be isolated from the freezing process occurring close to the attractive surfaces. Moreover, during the heating process, we observe minimal dependence at a strongly attractive surface.

Atomistics of pre-nucleation layering of liquid metals at the interface with poor nucleants

“…Thermodynamic analysis of pre-nucleation liquid layering. Revealing the mechanism of pre-nucleation liquid layering is a long-standing issue 8,9,[44][45][46][47][48][49] . In the following, we will analyse the liquid layering in the perspective of interfacial thermodynamics.…”

Crystal Nucleation in Liquids: Open Questions and Future Challenges in Molecular Dynamics Simulations

“…Finally, Zhang et al 274 recently probed the influence of structured and structureless LJ potential walls or nucleation rates. Both types of wall were found to increase the temperature at which nucleation occurs.…”

The Many Faces of Heterogeneous Ice Nucleation: Interplay Between Surface Morphology and Hydrophobicity

“…For this interaction strength the molecules essentially face a hard wall which in turn could even hinder nucleation compared to the homogeneous case 33,[76][77][78] . To understand this we must first mention, what happens for the homogeneous bulk case (which we term Homo) and the case of a free standing water slab (called Homo VAC ) with two water-vacuum interfaces.…”

“…For this adsorption energy the molecules basically face a hard wall which in turn could even hinder nucleation compared to the homogeneous case 33,[76][77][78] . By analyzing the distribution of pre-critical nuclei (see SI, Figure S8) we find that these avoid the neighborhood of the surface for mentioned E ads range.…”