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

Nucleation process is the most important stage in the formation of a crystal and has attracted the attention of researchers due to its importance in many technological and biological contexts. As the presence of impurities affects the nucleation process significantly, several studies have been made in the past to understand it. In this article is presented an overview of various studies made to understand the effect of soluble impurities on the crystal nucleation parameters of certain important materials in aqueous solution focusing the results reported by the research group of the present author.

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Nucleation Model for the Description of Glass Formation

Modern Physics Letters B ◽

10.1142/s0217984998000664 ◽

1998 ◽

Vol 12 (14n15) ◽

pp. 561-568 ◽

Cited By ~ 1

Author(s):

M. Micoulaut

Keyword(s):

Cooling Rate ◽

Glass Formation ◽

Dynamical Equation ◽

Stationary Solutions ◽

Crystal Nucleation ◽

Nucleation Process ◽

Nucleation Frequency ◽

Nucleation Model ◽

Temperature Transformation ◽

Kinetic Treatment

We present in this letter a model of glass formation using energy barriers and a crystal nucleation process. We then analyze the corresponding dynamical equation in the vicinity of the stationary solutions. The occurence of a pure amorphous solution (i.e. glass) is due to the contribution of a ratio depending on the cooling rate and the crystal nucleation frequency. We also construct time-temperature transformation (TTT) curves in order to relate the model with the kinetic treatment of glass formation.

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Urea homogeneous nucleation mechanism is solvent dependent

Faraday Discussions ◽

10.1039/c4fd00235k ◽

2015 ◽

Vol 179 ◽

pp. 291-307 ◽

Cited By ~ 31

Author(s):

Matteo Salvalaglio ◽

Marco Mazzotti ◽

Michele Parrinello

Keyword(s):

Finite Size ◽

Single Step ◽

Crystal Nucleation ◽

Primary Role ◽

Nucleation Process ◽

Polymorphic Transitions ◽

Dynamics Simulations ◽

A Minor ◽

Energy Surfaces ◽

The Impact

The composition of the mother phase plays a primary role in crystallization processes, affecting both crystal nucleation and growth. In this work, the influence of solvents on urea nucleation has been investigated by means of enhanced sampling molecular dynamics simulations. We find that, depending on the solvent, the nucleation process can either follow a single-step or a two-step mechanism. While in methanol and ethanol a single-step nucleation process is favored, in acetonitrile a two-step process emerges as the most likely nucleation pathway. We also find that solvents have a minor impact on polymorphic transitions in the early stages of urea nucleation. The impact of finite size effects on the free energy surfaces is systematically considered and discussed in relation to the simulation setup.

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Nucleation of pseudo hard-spheres and dumbbells at moderate metastability: appearance of A15 Frank–Kasper phase at intermediate elongations

Physical Chemistry Chemical Physics ◽

10.1039/c8cp04964e ◽

2019 ◽

Vol 21 (4) ◽

pp. 1656-1670 ◽

Cited By ~ 3

Author(s):

Itziar Zubieta ◽

Miguel Vázquez del Saz ◽

Pablo Llombart ◽

Carlos Vega ◽

Eva G. Noya

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Hard Spheres ◽

Crystal Nucleation ◽

Brute Force ◽

Dynamics Simulations

Crystal nucleation of repulsive hard-dumbbells from the sphere to the two tangent spheres limit is investigated at moderately high metastability by brute-force molecular dynamics simulations.

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Comparison of harmfulness between fluoride and cadmium ions on the crystal nucleation process

Bone ◽

10.1016/j.bone.2009.03.335 ◽

2009 ◽

Vol 44 ◽

pp. S414

Author(s):

M. Kakei ◽

T. Sakae ◽

H. Mishima ◽

M. Yoshikawa

Keyword(s):

Crystal Nucleation ◽

Nucleation Process ◽

Cadmium Ions

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The role of cracks in the crystal nucleation process of amorphous griseofulvin

The European Physical Journal Special Topics ◽

10.1140/epjst/e2016-60358-y ◽

2017 ◽

Vol 226 (5) ◽

pp. 837-847 ◽

Cited By ~ 11

Author(s):

J. F. Willart ◽

E. Dudognon ◽

A. Mahieu ◽

M. Eddleston ◽

W. Jones ◽

...

Keyword(s):

Crystal Nucleation ◽

Nucleation Process

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Insight into the role of pre-assembly and desolvation in crystal nucleation: a case of p-nitrobenzoic acid

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s2052520619009478 ◽

2019 ◽

Vol 75 (5) ◽

pp. 845-854

Author(s):

Shuyi Zong ◽

Jingkang Wang ◽

Hao Wu ◽

Qi Liu ◽

Yunhui Hao ◽

...

Keyword(s):

Crystal Structure ◽

Density Functional ◽

Structural Similarity ◽

Solution Chemistry ◽

Crystal Nucleation ◽

Energy Calculation ◽

Nucleation Process ◽

Nucleation Kinetics ◽

Nitrobenzoic Acid ◽

The Relationship

As one of the most important phenomena in crystallization, the crystal nucleation process has always been the focus of research. In this work, influences of pre-assembly species and the desolvation process on the crystal nucleation process were studied. p-Nitrobenzoic acid (PNBA) was taken as a model compound to investigate the relationship between solution chemistry and nucleation kinetics in seven different solvents. One unsolvated form and four solvates of PNBA were obtained and one of the solvates was newly discovered. The nucleation behaviours and nucleation kinetics of PNBA in the seven solvents were studied and analyzed. Density functional theory (DFT) and solvation energy calculation were adopted to evaluate the strength of solute–solvent interactions. Vibrational spectroscopy combined with molecular simulation was applied to reveal the pre-assembly species in the solution. Based on these results, a comprehensive understanding of the relationship between molecular structure, crystal structure, solution chemistry and nucleation dynamics was proposed and discussed. It was found that the structural similarity between solution chemistry and crystal structure, the interaction between specific sites and the overall strength of solvation will jointly affect the nucleation process.

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Concluding remarks

Faraday Discussions ◽

10.1039/c5fd00042d ◽

2015 ◽

Vol 179 ◽

pp. 543-547 ◽

Cited By ~ 7

Author(s):

Allan S. Myerson

Keyword(s):

Crystallization Process ◽

Crystal Form ◽

Nucleation Theory ◽

Crystal Nucleation ◽

Classical Nucleation Theory ◽

Nucleation Process ◽

Nucleation Mechanisms ◽

Process Work ◽

And Control ◽

Crystallization From Solution

Crystallization from solution is a crucial process used in the manufacture of a wide variety of materials. The first step in the crystallization process is the birth of a new crystalline phase, which is known as nucleation. Nucleation plays a key role in determining the results of any crystallization process with respect to the size, shape and crystal form obtained. Classical nucleation theory does not adequately explain the crystal nucleation process. Work described in the literature and at this Faraday Discussion describe more complex nucleation mechanisms which are generally known as two-step nucleation models. In addition, as most nucleation is influenced by dust, dirt and container surfaces, the importance of heterogeneous nucleation and the use of templates to accelerate nucleation and influence crystal form are promising methods for the study and control of nucleation. It is also clear from this Faraday Discussion that interest in this topic has grown, and new and novel experimental and modeling approaches are being used for the study of crystal nucleation from solution.

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Self-Avoiding Random Walks as a Model to Study Athermal Linear Polymers under Extreme Plate Confinement

Polymers ◽

10.3390/polym12040799 ◽

2020 ◽

Vol 12 (4) ◽

pp. 799

Author(s):

Oscar Parreño ◽

Pablo Miguel Ramos ◽

Nikos Ch. Karayiannis ◽

Manuel Laso

Keyword(s):

Random Walks ◽

Hard Spheres ◽

Configurational Entropy ◽

Polymer Chains ◽

Crystal Nucleation ◽

Face Centered Cubic ◽

Linear Polymers ◽

Parallel Plates ◽

Uniform Size ◽

Chain Conformations

Monte Carlo (MC) simulations, built around chain-connectivity-altering moves and a wall-displacement algorithm, allow us to simulate freely-jointed chains of tangent hard spheres of uniform size under extreme confinement. The latter is realized through the presence of two impenetrable, flat, and parallel plates. Extreme conditions correspond to the case where the distance between the plates approaches the monomer size. An analysis of the local structure, based on the characteristic crystallographic element (CCE) norm, detects crystal nucleation and growth at packing densities well below the ones observed in bulk analogs. In a second step, we map the confined polymer chains into self-avoiding random walks (SAWs) on restricted lattices. We study all realizations of the cubic crystal system: simple, body centered, and face centered cubic crystals. For a given chain size (SAW length), lattice type, origin of SAW, and level of confinement, we enumerate all possible SAWs (equivalently all chain conformations) and calculate the size distribution. Results for intermediate SAW lengths are used to predict the behavior of long, fully entangled chains through growth formulas. The SAW analysis will allow us to determine the corresponding configurational entropy, as it is the driving force for the observed phase transition and the determining factor for the thermodynamic stability of the corresponding crystal morphologies.

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Crystal, Fivefold and Glass Formation in Clusters of Polymers Interacting with the Square Well Potential

Polymers ◽

10.3390/polym12051111 ◽

2020 ◽

Vol 12 (5) ◽

pp. 1111

Author(s):

Miguel Herranz ◽

Manuel Santiago ◽

Katerina Foteinopoulou ◽

Nikos Ch. Karayiannis ◽

Manuel Laso

Keyword(s):

Local Density ◽

Hard Spheres ◽

Local Environment ◽

Crystal Nucleation ◽

Average Chain Length ◽

Model Parameters ◽

Face Centered Cubic ◽

Polymer Systems ◽

Hexagonal Close Packed ◽

Square Well

We present results, from Monte Carlo (MC) simulations, on polymer systems of freely jointed chains with spherical monomers interacting through the square well potential. Starting from athermal packings of chains of tangent hard spheres, we activate the square well potential under constant volume and temperature corresponding effectively to instantaneous quenching. We investigate how the intensity and range of pair-wise interactions affected the final morphologies by fixing polymer characteristics such as average chain length and tolerance in bond gaps. Due to attraction chains are brought closer together and they form clusters with distinct morphologies. A wide variety of structures is obtained as the model parameters are systematically varied: weak interactions lead to purely amorphous clusters followed by well-ordered ones. The latter include the whole spectrum of crystal morphologies: from virtually perfect hexagonal close packed (HCP) and face centered cubic (FCC) crystals, to random hexagonal close packed layers of single stacking direction of alternating HCP and FCC layers, to structures of mixed HCP/FCC character with multiple stacking directions and defects in the form of twins. Once critical values of interaction are met, fivefold-rich glassy clusters are formed. We discuss the similarities and differences between energy-driven crystal nucleation in thermal polymer systems as opposed to entropy-driven phase transition in athermal polymer packings. We further calculate the local density of each site, its dependence on the distance from the center of the cluster and its correlation with the crystallographic characteristics of the local environment. The short- and long-range conformations of chains are analyzed as a function of the established cluster morphologies.

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