Nature evolution of the shortened bond in atomic clusters and at junction interfaces

TL;DR

This paper investigates how bond nature evolution influences the thermal and mechanical properties of nanosolids and interfaces, explaining phenomena like superheating and size-dependent melting point oscillations.

Contribution

It reveals the critical role of bond nature evolution in the thermal stability and mechanical strength of nanoscale materials and interfaces, a novel insight into nanoscale thermodynamics.

Findings

Bond nature evolution causes superheating in small nanosolids.

Size-dependent melting point oscillations are explained by bond changes.

Chemically capped clusters exhibit increased melting points with decreasing size.

Abstract

Thermally stimulated process such as evaporation, phase transition, or solid-liquid transition of a solid consumes each a certain portion of the solid cohesive energy that is the sum of bond energy over all the coordinates of all the involved atoms. Generally, the critical temperatures for such processes drop with solid size, unless hetero capping or interfacial interaction becomes dominant, because of the increased portion of the lower-coordinated surface atoms [Sun et al., J. Phys. Chem. B108, 1080 (2004)]. It is intriguing, however, that the melting point (Tm) of a solid containing III-A or IV-A atoms oscillates with size (the Tm drops first and then rises as the solid size is reduced) and that the Tm of chemically capped nanosolid often increases with the inverse size. Here we show that bond nature evolution is essential for the selective nanosolids and at the junction interfaces, which is responsible for the superheating of the smallest nanosolids, chemically capped clusters, and junction interfaces that exhibit insulating nature with high mechanical strength.