Molecular dynamics methodology to investigate steady-state heterogeneous crystal growth (original) (raw)
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The Journal of Chemical Physics
Kinetics of crystal-growth is investigated along the solid-liquid coexistence line for the (100), (110) and (111) orientations of the Lennard-Jones and Weeks-Chandler-Andersen fcc crystal-liquid interface, using non-equilibrium molecular dynamics simulations. A slowing down of the growth kinetics along the coexistence line is observed, which is mostly a temperature effect, with other quantities such as the melting pressure and liquid self-diffusion coefficient having a negligible impact. The growth kinetics of the two potentials become similar at large values of the melting temperature and pressure, when both resemble a purely repulsive soft-sphere potential. Classical models of crystallization from the melt are in reasonable qualitative agreement with our simulation data. Finally, several one-phase empirical melting/freezing rules are studied with respect to their validity along the coexistence line.
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.
Journal of Molecular Graphics & Modelling, 2022
In this paper we report a successful molecular simulation study exploring the heterogeneous crystal growth of sI methane hydrate along its [001] crystallographic face. The molecular modeling of the crystal growth of methane hydrate has proven in the past to be very challenging, and a reasonable framework to overcome the difficulties related to the simulation of such systems is presented. Both the microscopic mechanisms of heterogeneous crystal growth as well as interfacial properties of methane hydrate are probed. In the presence of the appropriate crystal template, a strong tendency for water molecules to organize into cages around methane at the growing interface is observed; the interface also demonstrates a strong affinity for methane molecules. The maximum growth rate measured for a hydrate crystal is about 4 times higher than the value previously determined for ice I in a similar framework (
Crystallization of Liquid Water in a Molecular Dynamics Simulation
Physical Review Letters, 1994
In this Letter we report our success in crystallizing a bulk sample of liquid water in molecular dynamics simulations. In these computer experiments supercooled liquid TIP4P water at 250 K was subjected to a homogeneous static electric field; the resulting polar crystal which forms within 200 ps has the structure of ice I,. These simulation results suggest that the local electric fields that exist near the surfaces of various materials or within confined geometries can play an important role in promoting the crystallization of liquid water.
Molecular Physics, 1996
The melting of structure I methane clathrate hydrate has been investigated using NVT molecular dynamics simulations, for a number of potential energy models for water and methane. The equilibrated hydrate crystal has been heated carefully from 270 K, in steps of 5 K, until a well de® ned phase instability appears. At a density of 0± 92 g cm Õ $ , an upper bound for the mechanical stability of the methane hydrate lattice over a timescale of 11 nanoseconds is 330 K. Finite size eOE ects have been investigated by simulating systems of 1 and 8 units cells of methane hydrate. The properties of the melted system upon cooling are examined.
Computer simulations of heterogeneous crystal growth of atomic systems
Molecular Physics, 2005
The systematic study of the mechanisms of heterogeneous crystal growth has proven somewhat difficult. Here we briefly review previous work in this area. We then report a novel molecular dynamics simulation methodology that has been developed to enable the creation of steady-state crystal growth-melting. We employ this methodology to examine BCC and FCC 001, 011 and 111 crystal faces of systems of spherical particles interacting through Lennard-Jones and inverse sixth-power potentials. Various growth-melting conditions are explored involving different temperature gradients and velocities. Profile functions of various quantities across the interface have been recorded; as measured in the moving frame by the present approach, these functions are effectively averaged over the molecular detail of the interface and become smooth. This characteristic allows for new ways of interpreting profile functions like the energy and local structural order parameters. We find that when the derivative of these profile functions is taken with respect to the z dimension, we obtain consistent peaks that characterize the freezing-melting interfaces. Consequently, the position and width of an interface are easily identified. The interfacial widths calculated show that it is somewhat dependent on the temperature gradient but no dependence on the growth velocity was observed. The interfacial widths are found to decrease in the order 001 >011 > 111. Furthermore we determine interfacial tensions, which arise directly out of our methodology. We are able to demonstrate that ordering and disordering are distinct and different processes occurring at both the melting and freezing interfaces.
Molecular dynamics simulation of ice growth from supercooled pure water and from salt solution
Annals of Glaciology, 2006
The kinetics of ice growth on the prismatic and basal planes is studied by molecular dynamics simulations. The time evolution of two systems has been investigated. In one a slab of ice is initially in contact with supercooled water, while in the second the ice is in contact with a supercooled salt solution. The simulations were done at a temperature below the eutectic temperature, and complete solidification is observed. The total freezing time is longer in the systems with ions than in the systems with pure water. The final state for the salt systems always shows the formation of ion clusters. For the ionic system growing on the prismatic plane, an intermediate metastable state is observed before total solidification. The duration of this metastable state depends on the ability of the system to get all the ions participating in cluster formation. The simulations enable understanding of the mechanisms for ice formation under different solution conditions.
The molecular dynamics (MD) simulation technique is a powerful tool for the investigation of multicomponent liquids and solids. A realistic description of such systems relies on the quality of the effective potential with which the interactions between the atoms are modelled in a MD simulation. We propose a fitting scheme to derive effective potentials from ab initio simulations. This scheme is used to parametrize a new potential for silica. In a second case study, MD simulations are used to investigate crystallization in an AlNi alloy, elucidating the crystal growth mechanism on an atomistic scale.
Journal of Computational Physics, 2005
A phase-field model for non-isothermal solidification in multicomponent systems [SIAM J. Appl. Math. 64 (3) (2004) 775-799] consistent with the formalism of classic irreversible thermodynamics is used for numerical simulations of crystal growth in a pure material. The relation of this approach to the phase-field model by Bragard et al. [Interface Science 10 (2-3) (2002) 121-136] is discussed. 2D and 3D simulations of dendritic structures are compared with the analytical predictions of the Brener theory [
The Journal of Chemical Physics, 2020
Kinetic rate factors of crystallization have a direct effect on formation and growth of an ordered solid phase in supercooled liquids and glasses. Using crystallizing Lennard-Jones liquid as an example, in the present work we perform a direct quantitative estimation of values of the key crystallization kinetic rate factors-the rate g + of particle attachments to a crystalline nucleus and the rate g − of particle detachments from a nucleus. We propose a numerical approach, according to which a statistical treatment of the results of molecular dynamics simulations was performed without using any model functions and/or fitting parameters. This approach allows one to accurately estimate the critical nucleus size n c. We find that for the growing nuclei, whose sizes are larger than the critical size n c , the dependence of these kinetic rate factors on the nucleus size n follows a power law. In the case of the subnucleation regime, when the nuclei are smaller than n c , the n-dependence of the quantity g + is strongly determined by the inherent microscopic properties of a system and this dependence cannot be described in the framework of any universal law (for example, a power law). It has been established that the dependence of the growth rate of a crystalline nucleus on its size goes into the stationary regime at the sizes n > 3n c particles.