The early crystal nucleation process in hard spheres shows synchronised ordering and densification

Berryman, Joshua T.; Anwar, Muhammad; Dorosz, Sven; Schilling, Tanja

doi:10.1063/1.4953550

Cited by 27 publications

(23 citation statements)

References 34 publications

(50 reference statements)

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“…A very recent [140] re-analysis of the simulation trajectories of Ref. [109] ("density-first" case) showed a simultaneous increase of density and bond-orientational order leading up to nucleation.…”

Section: Translational Vs Orientational Order Curvesmentioning

confidence: 99%

Crystal nucleation as the ordering of multiple order parameters

Russo

Tanaka

2016

The Journal of Chemical Physics

105

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Nucleation is an activated process in which the system has to overcome a free energy barrier in order for a first-order phase transition between the metastable and the stable phases to take place. In the liquid-to-solid transition the process occurs between phases of different symmetry, and it is thus inherently a multi-dimensional process, in which all symmetries are broken at the transition. In this Focus Article, we consider some recent studies which highlight the multi-dimensional nature of the nucleation process. Even for a single-component system, the formation of solid crystals from the metastable melt involves fluctuations of two (or more) order parameters, often associated with the decoupling of positional and orientational symmetry breaking. In other words, we need at least two order parameters to describe the free-energy of a system including its liquid and crystalline states. This decoupling occurs naturally for asymmetric particles or directional interactions, focusing here on the case of water, but we will show that it also affects spherically symmetric interacting particles, such as the hard-sphere system. We will show how the treatment of nucleation as a multi-dimensional process has shed new light on the process of polymorph selection, on the effect of external fields on the nucleation process, and on glass-forming ability.

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Section: Translational Vs Orientational Order Curvesmentioning

confidence: 99%

Crystal nucleation as the ordering of multiple order parameters

Russo

Tanaka

2016

The Journal of Chemical Physics

105

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“…Part of the scientific community believes that density fluctuations in the supersaturated fluid lead to local denser amorphous regions. 18,19 Others, instead, believe that bond-orientational order fluctuations lead to the formation of orientationally ordered structures. 15,[20][21][22] Another controversial topic concerns the rate of crystal nucleation.…”

Section: Introductionmentioning

confidence: 99%

The effect of hydrodynamics on the crystal nucleation of nearly hard spheres

Fiorucci

Coli

Padding

et al. 2020

The Journal of Chemical Physics

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We investigate the effect of hydrodynamic interactions (HIs) on the crystal nucleation of hard-sphere colloids for varying supersaturations. We use molecular dynamics and stochastic rotation dynamics techniques to account for the HIs. For high supersaturation values, we perform brute force simulations and compute the nucleation rate, obtaining good agreement with previous studies where HIs were neglected. In order to access low supersaturation values, we use a seeding approach method and perform simulations with and without HIs. We compute the nucleation rates for the two cases and surprisingly find good agreement between them. The nucleation rate in both cases follows the trend of the previous numerical results, thereby corroborating the discrepancy between experiments and simulations. Furthermore, we investigate the amount of fivefold symmetric clusters (FSCs) in a supersaturated fluid under different physical conditions, following the idea that FSCs compete against nucleation. To this end, we explore the role of the softness of the pair interactions, different solvent viscosities, and different sedimentation rates in simulations that include HIs. We do not find significant variations in the amount of FSCs, which might reflect the irrelevance of these three features on the nucleation process.

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“…However, for the liquid to solid transition the distinction of the phases in terms of order parameters is very different: with crystallization both the translational and orientational symmetry of the liquid is broken [34], and there is an accompanying density change (see e.g. [35] for a simulation study of synchronized ordering and densification). Clearly, such considerations must enter a first-principles discussion of crystal nucleation, but this is beyond the scope of the present work, which focusses on the effect that the nucleus shape is in general nonspherical.…”

Section: Introduction and Overviewmentioning

confidence: 99%

Free-energy barriers for crystal nucleation from fluid phases

et al. 2017

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Monte Carlo simulations of crystal nuclei coexisting with the fluid phase in thermal equilibrium in finite volumes are presented and analyzed, for fluid densities from dense melts to the vapor. Generalizing the lever-rule for two-phase coexistence in the canonical ensemble to finite volume, "measurements" of the nucleus volume together with the pressure and chemical potential of the surrounding fluid allows to extract the surface free energy of the nucleus. Neither the knowledge of the (in general non-spherical) nucleus shape nor of the angle-dependent interface tension is required for this task. The feasibility of the approach is demonstrated for a variant of the Asakura-Oosawa model for colloid-polymer mixtures, which form face-centered cubic colloidal crystals. For a polymer to colloid size ratio of 0.15, the colloid packing fraction in the fluid phase can be varied from melt values to zero by the variation of an effective attractive potential between the colloids. It is found that the approximation of spherical crystal nuclei often underestimates actual nucleation barriers significantly. Nucleation barriers are found to scale as ∆F * = (4π/3) 1/3γ (V * ) 2/3 + const. with the nucleus volume V * , and the effective surface tensionγ that accounts implicitly for the nonspherical shape can be precisely estimated.

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The early crystal nucleation process in hard spheres shows synchronised ordering and densification

Cited by 27 publications

References 34 publications

Crystal nucleation as the ordering of multiple order parameters

Crystal nucleation as the ordering of multiple order parameters

The effect of hydrodynamics on the crystal nucleation of nearly hard spheres

Free-energy barriers for crystal nucleation from fluid phases

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