Controlling anisotropy in 2D microscopic models of growth

TL;DR

This paper investigates how to control and quantify interface anisotropy in 2D lattice models, providing methods to tune interface energy and analyze growth patterns relevant to nanoscale non-equilibrium processes.

Contribution

It introduces a broken-bond model for calculating surface stiffness and line tension anisotropy in a 2D Ising model, supported by Monte Carlo simulations and a smoothing parameter for experimental resolution.

Findings

Minimal stiffness anisotropy conditions identified

Quantitative agreement with Monte Carlo simulations achieved

A smoothing parameter mimics experimental microscopy resolution

Abstract

The quantitative knowledge of interface anisotropy in lattice models is a major issue, both for the parametrization of continuum interface models, and for the analysis of experimental observations. In this paper, we focus on the anisotropy of line tension and stiffness, which plays a major role both in equilibrium shapes and fluctuations, and in the selection of nonequilibrium growth patterns. We consider a 2D Ising Hamiltonian on a square lattice with first and second-nearest-neighbor interactions. The surface stiffness and line tension are calculated by means of a broken-bond model for arbitrary orientations. The analysis of the interface energy allows us to determine the conditions under which stiffness anisotropy is minimal. These results are supported by a quantitative comparison with kinetic Monte Carlo simulations, based on the coupling of a field of mobile atoms to a condensed phase. Furthermore, we introduce a generic smoothing parameter which allows one to mimic the finite resolution of experimental microscopy techniques. Our results provide a method to fine-tune the interface energy in models of nanoscale non-equilibrium processes, where anisotropy and fluctuations combine and give rise to non-trivial morphologies.