# Hydrodynamic theory of freezing: Nucleation and polycrystalline growth

## TL;DR

This paper presents a hydrodynamic theory combining fluctuating hydrodynamics and phase-field crystal models to explore crystal nucleation and polycrystalline growth, revealing mechanisms for grain formation and spherulite-like structures.

## Contribution

It introduces a novel hydrodynamic approach to simulate various nucleation processes and growth front phenomena in undercooled liquids, including grain orientation and defect formation.

## Key findings

- Growth front nucleation leads to new grain orientations.
- Dislocation formation occurs at the solid-liquid interface.
- Density wave interference causes spherulite-like nanostructures.

## Abstract

Structural aspects of crystal nucleation in undercooled liquids are explored using a nonlinear hydrodynamic theory of crystallization proposed recently [G. I. Toth et al., J. Phys.: Condens. Matter 26, 055001 (2014)], which is based on combining fluctuating hydrodynamics with the phase-field crystal theory. We show that in this hydrodynamic approach not only homogeneous and heterogeneous nucleation processes are accessible, but also growth front nucleation, which leads to the formation of new (differently oriented) grains at the solid-liquid front in highly undercooled systems. Formation of dislocations at the solid-liquid interface and interference of density waves ahead of the crystallization front are responsible for the appearance of the new orientations at the growth front that lead to spherulite-like nanostructures.