Crystallization of Soft Matter under Confinement at Interfaces and in Wedges.

0466471 - ÚCHP 2017 RIV GB eng J - Journal Article
Archer, A.J. - Malijevský, Alexandr
Crystallization of Soft Matter under Confinement at Interfaces and in Wedges.
Journal of Physics-Condensed Matter. Roč. 28, č. 24 (2016), s. 244017. ISSN 0953-8984. E-ISSN 1361-648X
R&D Projects: GA ČR GA13-09914S
Institutional support: RVO:67985858
Keywords : classical density functional theory * interfacial phase behaviour * surface freezing
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 2.678, year: 2016

The surface freezing and surface melting transitions that are exhibited by a model two-dimensional soft matter system are studied. The behaviour when confined within a wedge is also considered. The system consists of particles interacting via a soft purely repulsive pair potential. Density functional theory (DFT) is used to calculate density profiles and thermodynamic quantities. The external potential due to the confining walls is modelled via a hard wall with an additional repulsive Yukawa potential. The surface phase behaviour depends on the range and strength of this repulsion: when the repulsion is weak, the wall promotes freezing at the surface of the wall. The thickness of this frozen layer grows logarithmically as the bulk liquid-solid phase coexistence is approached. Our mean-field DFT predicts that this crystalline layer at the wall must be nucleated (i.e. there is a free energy barrier) and its formation is necessarily a first-order transition, referred to as prefreezing, by analogy with the prewetting transition. However, in contrast to the latter, prefreezing cannot terminate in a critical point, since the phase transition involves a change in symmetry. If the wall-fluid interaction is sufficiently long ranged and the repulsion is strong enough, surface melting can occur instead. Then the interface between the wall and the bulk crystalline solid is wetted by the liquid phase as the chemical potential is decreased towards the value at liquid-solid coexistence. It is observed that the finite thickness fluid film at the wall has a broken translational symmetry due to its proximity to the bulk crystal, and so the nucleation of the wetting film can be either first order or continuous. Our mean-field theory predicts that for certain wall potentials there is a premelting critical point analogous to the surface critical point for the prewetting transition.
Permanent Link: http://hdl.handle.net/11104/0264748