Controlling the shape of small clusters with and without macroscopic fields

TL;DR

This paper explores strategies to control the shape of nano-clusters efficiently, using external fields and temperature optimization, with potential applications in atomic, colloidal, and nanoparticle systems.

Contribution

It introduces a numerical approach to minimize the time to achieve a target cluster shape, considering external fields and temperature effects, filling a gap in theoretical control methods.

Findings

Optimal temperature exists for shape formation without external field.

External fields can significantly reduce the shape formation time.

Time gain increases with cluster size and lower temperature.

Abstract

Despite major advances in the understanding of the formation and dynamics of nano-clusters in the past decades, theoretical bases for the control of their shape are still lacking. We investigate strategies for driving fluctuating few-particle clusters to an arbitrary target shape in minimum time with or without an external field. This question is recast into a first passage problem, solved numerically, and discussed within a high temperature expansion. Without field, large-enough low-energy target shapes exhibit an optimal temperature at which they are reached in minimum time. We then compute the optimal way to set an external field to minimize the time to reach the target, leading to a gain of time that grows when increasing cluster size or decreasing temperature. This gain can shift the optimal temperature or even create one. Our results could apply to clusters of atoms at equilibrium, and colloidal or nanoparticle clusters under thermo- or electrophoresis.