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

Abstract

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.

Hydrodynamic and frictional modulation of deformations in switchable colloidal crystallites

“…That said, the impact of hydrodynamics on the overall rate of transformation is not dramatic, corresponding to about a factor of 2 or less in either direction relative to simple BD. Interestingly, this finding is consistent with the results of recent studies that conclude hydrodynamic interactions do not substantially affect overall nucleation rates of nearly hard sphere crystals (37,38). The relatively weak effect of hydrodynamic interactions on the overall transformation dynamics is not inconsistent with the strong effect on the outcome of the transformation.…”

Parasitic crystallization of colloidal electrolytes: growing a metastable crystal from the nucleus of a stable phase

“…Nonetheless, discrepancies in the nucleation rate of common substances, such as water, are currently under debate, not only between different simulation techniques 39,55,56 but also among different experimental setups. 5,6,57 Likewise, in hard-sphere colloidal crystal nucleation, a long-standing discrepancy among crystal nucleation rates from experiments and computer simulations still persists, 11,58,59 although several possible explanations have been recently discussed such as heterogeneous nucleation, 60 incomplete shear melting, 61 hydrodynamic effects on the crystal growth 62 and the nucleation rate 63,64 or sedimentation. 65,66 In addition to these methodological, and experimental vs. numerical discrepancies in the nucleation rates of these systems, there is also a general debate in the nucleation community about the validity of Classical Nucleation Theory (CNT) 67,68 to successfully describe nucleation in widely diverse scenarios.…”

Fcc vs. hcp competition in colloidal hard-sphere nucleation: on their relative stability, interfacial free energy and nucleation rate

“…Moreover, a very good agreement with previous Umbrella Sampling [28,30] and Forward Flux Sampling calculations [30] of pure HS is achieved, exhibiting again the reliability of the chosen local order parameter [126] and the mislabelling criterion [55,137] within the Seeding framework. Nucleation rates considering hydrodynamic effects for the Weeks-Chandler-Andersen (WCA) model [139] at moderate [140] and very high [141] pressure are also depicted in Fig. 4, the former obtained by means of Seeding (of fcc clusters) simulations, and the later through Brute force simulations.…”

“…Umbrella, Forward Flux Sampling and brute force nucleation rates (maroon empty symbols) for standard HS are also included [28,30]. Moreover, computational nucleation rates considering hydrodynamic effects are also plotted (purple empty symbols) [140,141]. Blue symbols indicate experimental nucleation rates from different authors [11][12][13].…”