The Mechanism of the Ultra-Fast Crystal Growth of Pure Metals from their Melts

TL;DR

This paper investigates the ultra-fast crystal growth of pure metals from melts, revealing that such growth occurs without activation barriers, contrasting with traditional theories, through computer simulations that clarify the underlying kinetics.

Contribution

It provides a physical explanation for barrierless crystal growth in metals, challenging classic crystal growth theories using computational simulations.

Findings

Growth rates reach 70 meters per second.

Crystallization occurs without activation barriers.

Diffusion in liquid metals is thermally activated, but ordering into crystals is not.

Abstract

A crystal of pure nickel grows from its melt at a rate that reaches 70 meters per second. This extraordinary growth rate has led to the suggestion that metallic crystals might provide the next generation of phase change materials. The huge crystal growth rates of metals are a consequence of kinetics without activated control, in sharp contrast to the prediction of the classic theory of crystal growth. While the existence of growth kinetics without barriers is now well established in atomic melts, no physical explanation for the absence of an activation barrier to ordering has been established. It is something of a paradox that diffusion in the liquid metal is governed by thermal activation while the movement of the same atoms as they organize into a crystal is not. In this paper we use computer simulations of crystallization in pure metals to explicitly resolve the origin of the growth kinetics without barriers.