Deposition control of model glasses with surface-mediated orientational order

TL;DR

This paper presents a minimal model for anisotropic molecules that exhibits surface orientational order without bulk order, and demonstrates how designed protocols can produce uniform nonequilibrium structures.

Contribution

It introduces a minimal theoretical model and protocol design methods to control surface and bulk order in anisotropic molecular deposition.

Findings

Surface order exists without bulk order in the model.

Oscillatory protocols can produce uniform nonequilibrium structures.

Growth-poisoning mechanisms affect deposition dynamics.

Abstract

We introduce a minimal model of solid-forming anisotropic molecules that displays, in thermal equilibrium, surface orientational order without bulk orientational order. The model reproduces the nonequilibrium behavior of recent experiments in that a bulk nonequilibrium structure grown by deposition contains regions of orientational order characteristic of the surface equilibrium. This order is deposited in general in a nonuniform way, because of the emergence of a growth-poisoning mechanism that causes equilibrated surfaces to grow slower than non-equilibrated surfaces. We use evolutionary methods to design oscillatory protocols able to grow nonequilibrium structures with uniform order, demonstrating the potential of protocol design for the fabrication of this class of materials.