No abstract

Motivated by experimental reports of higher-than-bulk melting temperatures in small gallium clusters, we perform first-principles molecular dynamics simulations of Ga(20) and Ga(20)(+) using parallel tempering in the microcanonical ensemble. The respective specific heat (C(V)) curves, obtained using the multiple histogram method, exhibit a broad peak centered at approximately 740 and 610 K--well above the melting temperature of bulk gallium (303 K) and in reasonable agreement with experimental data for Ga(20)(+). Assessment of atomic mobility confirms the transition from solid-like to liquid-like states near the C(V) peak temperature. Parallel tempering molecular dynamics simulations yield low-energy isomers that are ~0.1 eV lower in energy than previously reported ground state structures, indicative of an energy landscape with multiple, competing low-energy morphologies. Electronic structure analysis shows no evidence of covalent bonding, yet both the neutral and charged clusters exhibit greater-than-bulk melting temperatures.

In nature, snowflake ice crystals arrange themselves into diverse symmetrical six-sided structures. We show an analogy of this when zinc (Zn) dissolves and crystallizes in liquid gallium (Ga). The low-melting-temperature Ga is used as a “metallic solvent” to synthesize a range of flake-like Zn crystals. We extract these metallic crystals from the liquid metal solvent by reducing its surface tension using a combination of electrocapillary modulation and vacuum filtration. The liquid metal–grown crystals feature high morphological diversity and persistent symmetry. The concept is expanded to other single and binary metal solutes and Ga-based solvents, with the growth mechanisms elucidated through ab initio simulation of interfacial stability. This strategy offers general routes for creating highly crystalline, shape-controlled metallic or multimetallic fine structures from liquid metal solvents.