Classical nucleation theory in the phase-field crystal model

Phase field crystal models with applications to laser deposition: A review

In this article, we address the application of phase field crystal (PFC) theory, a hybrid atomistic-continuum approach, for modeling nanostructure kinetics encountered in laser deposition. We first provide an overview of the PFC methodology, highlighting recent advances to incorporate phononic and heat transport mechanisms. To simulate laser heating, energy is deposited onto a number of polycrystalline, two-dimensional samples through the application of initial stochastic fluctuations. We first demonstrate the ability of the model to simulate plasticity and recrystallization events that follow laser heating in the isothermal limit. Importantly, we also show that sufficient kinetic energy can cause voiding, which serves to suppress shock propagation. We subsequently employ a newly developed thermo-density PFC theory, coined thermal field crystal (TFC), to investigate laser heating of polycrystalline samples under non-isothermal conditions. We observe that the latent heat of transition associated with ordering can lead to long lasting metastable structures and defects, with a healing rate linked to the thermal diffusion. Finally, we illustrate that the lattice temperature simulated by the TFC model is in qualitative agreement with predictions of conventional electron-phonon two-temperature models. We expect that our new TFC formalism can be useful for predicting transient structures that result from rapid laser heating and re-solidification processes.

Atomistic simulation model on a diffusive timescale based on the extension of the cluster-activation method to continuous space

Recently the phase-field crystal method has attracted considerable attention because it can simulate the atomic behavior of a system on a diffusive timescale. In this study an atomistic simulation model is proposed, which is an extension of the cluster-activation method (CAM) from discrete to continuous space. This approach, called the continuous CAM, can simulate various physical phenomena of atomistic systems on diffusive timescales and employs well-defined atomistic properties, such as interatomic interaction energies, as the main input parameters. The versatility of the continuous CAM was investigated by performing simulations of crystal growth in an undercooled melt, homogeneous nucleation during solidification, and formation of grain boundaries in pure metal.

Solidification of Undercooled Liquid under Supergravity Field by Phase-Field Crystal Approach

Solidification under a supergravity field is an effective method to control the solidified microstructure, which can be used to prepare materials with excellent comprehensive properties. In order to explore the influence of supergravity on the solidification behavior, a phase-field crystal model for the solidification under supergravity fields is developed and utilized to study the supergravity-controlled solidification behaviors. The results show that the grains in the solidification structures are refined in a supergravity field. The grain size in a zero-gravity field is uniformly distributed in the sample, but gradually decreases along the direction of the supergravity, showing a graded microstructure. The simulations show real-time images of the nucleation and growth of grains during solidification. In a supergravity field, solidification occurs preferentially in the liquid subject to greater gravity and advances in the opposite direction of supergravity with the time evolution. In addition, the driving force of crystallization in liquid is calculated to explain the effect of the supergravity field on the solidification structure from a thermodynamic point of view. Our findings are expected to provide a new approach and insight for understanding the solidification behaviors under supergravity.