Dissipation in a Crystallization Process (original) (raw)

Crystal growth from a supersaturated melt: Relaxation of the solid-liquid dynamic stiffness

The Journal of Chemical Physics, 2014

We discuss the growth process of a crystalline phase out of a metastable over-compressed liquid that is brought into contact with a crystalline substrate. The process is modeled by means of molecular dynamics. The particles interact via the Lennard-Jones potential and their motion is locally thermalized by Langevin dynamics. We characterize the relaxation process of the solid-liquid interface, showing that the growth speed is maximal for liquid densities above the solid coexistence density, and that the structural properties of the interface rapidly converge to equilibrium-like properties. In particular, we show that the off-equilibrium dynamic stiffness can be extracted using capillary wave theory arguments, even if the growth front moves fast compared to the typical diffusion time of the compressed liquid, and that the dynamic stiffness converges to the equilibrium stiffness in times much shorter than the diffusion time.

Dissipation by a crystallization process

EPL (Europhysics Letters), 2016

Roles of bond orientational ordering in glass transition and crystallization Hajime Tanaka Crystallization in three-and two-dimensional colloidal suspensions U Gasser Crystallization in suspensions of hard spheres: a Monte Carlo and molecular dynamicssimulation study T Schilling, S Dorosz, H J Schöpe et al. Out-of-equilibrium processes in suspensions of oppositely charged colloids: liquid-to-crystalnucleation and gel formation

On the mesoscopic description of locally nonequilibrium solidification of pure substances

JETP Letters, 2015

A phase field model of locally nonequilibrium solidification of a supercooled melt of a pure substance has been proposed. To derive thermodynamically consistent equations of the model, the method of extended irre versible thermodynamics has been used. It has been assumed that Gibbs potentials describing thermodynam ically equilibrium states in terms of experimental data are known. The limit of a sharp interface of the model has been considered and an analytical dependence of the velocity of a flat solidification front on the temper ature has been obtained.

Equiaxed dendritic solidification in supercooled melts

Journal of Crystal Growth, 1999

The growth of equiaxed dendrites from a pure supercooled melt is examined. We propose modifications to the classical Ivantsov theory that allow for consideration of multiple interacting dendrites. The modified theory reveals the existence of a steady-state dendritic solidification mode in a frame of reference moving with the dendrite tip. This regime should be valid from the onset of nucleation to the commencement of time-dependent coarsening when the mass of the solid becomes comparable to the liquid mass in the solidification chamber. This regime is characterized by a reduced (relative to the single dendrite case) heat flux leading to slower solidification rates, but with the same level of supercooling. We study the effects of the relative proximity and number of interacting dendrites through a numerical example of solidification of succinonitrile, a common material used in many experiments. The data show that the model predicts a new steady growth regime that is different than the steady growth law of a single dendrite as described by Ivantsov theory.

Collective modes in simple melts: Transition from soft spheres to the hard sphere limit

Scientific Reports, 2017

We study collective modes in a classical system of particles with repulsive inverse-power-law (IPL) interactions in the fluid phase, near the fluid-solid coexistence (IPL melts). The IPL exponent is varied from n = 10 to n = 100 to mimic the transition from moderately soft to hard-sphere-like interactions. We compare the longitudinal dispersion relations obtained using molecular dynamic (MD) simulations with those calculated using the quasi-crystalline approximation (QCA) and find that this simple theoretical approach becomes grossly inaccurate for n\,\gtrsim 20$$ n ≳ 20 . Similarly, conventional expressions for high-frequency (instantaneous) elastic moduli, predicting their divergence as n increases, are meaningless in this regime. Relations of the longitudinal and transverse elastic velocities of the QCA model to the adiabatic sound velocity, measured in MD simulations, are discussed for the regime where QCA is applicable. Two potentially useful freezing indicators for classical...

Melting of a colloidal crystal

Physica A: Statistical Mechanics and its Applications

A melting transition for a system of hard spheres interacting by a repulsive Yukawa potential of DLVO form is studied. To find the location of the phase boundary, we propose a simple theory to calculate the free energies for the coexisting liquid and solid. The free energy for the liquid phase is approximated by a virial expansion. The free energy of the crystalline phase is calculated in the spirit of the Lenard-Jonnes and Devonshire (LJD) theory. The phase boundary is found by equating the pressures and chemical potentials of the coexisting phases. When the approximation leading to the equation of state for the liquid breakes down, the first order transition line is also obtained by applying the Lindemann criterion to the solid phase. Our results are then compared with the Monte Carlo simulations.

Crystal nucleation in a supercooled liquid with glassy dynamics

Physical review letters, 2009

In simulations of supercooled, high-density liquid silica we study a range of temperature T in which we find both crystal nucleation, as well as the characteristic dynamics of a glass forming liquid, including a breakdown of the Stokes-Einstein relation. We find that the liquid cannot be observed below a homogeneous nucleation limit (HNL) at which the liquid crystallizes faster than it can equilibrate. We show that the HNL would occur at lower T , and perhaps not at all, if the Stokes-Einstein relation were obeyed, and hence that glassy dynamics plays a central role in setting a crystallization limit on the liquid state in this case. We also explore the relation of the HNL to the Kauzmann temperature, and test for spinodal-like effects near the HNL.