Structural transformations in Cu, Ag, and Au metal nanoclusters

TL;DR

This study investigates the temperature-dependent structural transformations of Cu, Ag, and Au nanoclusters using a combined computational approach, revealing different transformation types and system-specific structural behaviors.

Contribution

It introduces a combined HSA and PTMD methodology to accurately study nanocluster structures across all temperatures, including melting, and analyzes system-specific differences.

Findings

Three main types of structural transformations identified.

Global minimum dominance varies with temperature.

Distinct behaviors observed across Cu, Ag, and Au nanoclusters.

Abstract

Finite-temperature structures of Cu, Ag, and Au metal nanoclusters are calculated in the entire temperature range from 0 K to melting using a computational methodology that we proposed recently [Settem \emph{et al.}, Nanoscale, 2022, 14, 939]. In this method, Harmonic Superposition Approximation (HSA) and Parallel Tempering Molecular Dynamics (PTMD) are combined in a complementary manner. HSA is accurate at low temperatures and fails at higher temperatures. PTMD, on the other hand, effectively samples the high temperature region and melting. This method is used to study the size- and system-dependent competition between various structural motifs of Cu, Ag, and Au nanoclusters in the size range 1 to 2 nm. Results show that there are mainly three types of structural changes in metal nanoclusters depending on whether a solid-solid transformation occurs. In the first type, global minimum is the dominant motif in the entire temperature range. In contrast, when a solid-solid transformation occurs, the global minimum transforms either completely to a different motif or partially resulting in a co-existence of multiple motifs. Finally, nanocluster structures are analyzed to highlight the system-specific differences across the three metals.