Crystallization of alkanes under quiescent and shearing conditions

Jabbarzadeh, Ahmad; Tanner, Roger I.

doi:10.1016/j.jnnfm.2009.02.008

Cited by 47 publications

(57 citation statements)

References 29 publications

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“…where the subscript α denotes the Cartesian component which can be X, Y or Z. θ α is the angle between the α axis of the simulation box and the chord vector which connects every other pair of carbon atoms in a same molecule [55] , shown in the upper inset of Fig.6. The order parameter can range from −0.5 (full order perpendicular to α axis) to 1.0 (full order parallel to α axis), with a value of 0 in the case of isotropic orientation (see the lower inset in Fig.6).…”

Section: Shear Induced Ordered Structure Of the Confined N-hexadecanementioning

confidence: 99%

The unique properties of the solid-like confined liquid films: A large scale molecular dynamics simulation approach

Wang

Zhao

2011

Acta Mechanica Solida Sinica

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The properties of the confined liquid are dramatically different from those of the bulk state, which were reviewed in the present work. We performed large-scale molecular dynamics simulations and full-atom nonequilibrium molecular dynamics simulations to investigate the shear response of the confined simple liquid as well as the n-hexadecane ultrathin films. The shear viscosity of the confined simple liquid increases with the decrease of the film thickness. Apart from the well-known ordered structure, the confined n-hexadecane exhibited a transition from 7 layers to 6 in our simulations while undergoing an increasing shear velocity. Various slip regimes of the confined n-hexadecane were obtained. Viscosity coefficients of individual layers were examined and the results revealed that the local viscosity coefficient varies with the distance from the wall. The individual n-hexadecane layers showed the shear-thinning behaviors which can be correlated with the occurrence of the slip. This study aimed at elucidating the detailed shear response of the confined liquid and may be used in the design and application of micro-and nano-devices.

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Section: Shear Induced Ordered Structure Of the Confined N-hexadecanementioning

confidence: 99%

The unique properties of the solid-like confined liquid films: A large scale molecular dynamics simulation approach

Wang

Zhao

2011

Acta Mechanica Solida Sinica

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“…These properties depend on the morphology of the semicrystalline state, i.e. on the distribution of crystallites sizes and shapes, which is in turn caused by the crystallization process [1]. In the last seven decades a large amount of work has been done to understand the crystallization of polymers but still there are a number of question which are either unanswered or controversially answered [2,3].…”

Section: Introductionmentioning

confidence: 99%

Crystallization of polyethylene: A molecular dynamics simulation study of the nucleation and growth mechanisms

Anwar

Schilling

2015

Polymer

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a b s t r a c tWe have performed molecular dynamics simulations to study the mechanism of crystallization from an undercooled polyethylene (C500) melt. We observe that crystal nucleation is initiated by the alignment of chain segments, which is followed by straightening of the chains and densification. Growth procedes via alignment of segments, which are in the vicinity of the growth front, with the chains in the crystalline lamella. Once chains are attached, the lamella thickens by sliding of the segments along the long axis of the chain from the amorphous regions into the crystalline regions. We do not observe the formation of any folded precursors.

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“…5,11 Their model exhibited good agreement with experimental data, in support of the viewpoint that FEN can be explained by flow-induced entropy reduction in the melt; however, it must be considered to be a phenomenological model due to its rigid assumptions about the nucleus shape and its reliance on unknown thermodynamic parameters. At the molecular level, there have been simulation efforts using both Monte Carlo (MC) [13][14][15] and Molecular Dynamics (MD) [16][17][18][19][20][21] to study FIC; however, relatively few focused specifically on the kinetics of nucleation. 22 Given that nucleation is a transient event, a MC simulation cannot accurately capture its kinetics without an enormous amount of prior knowledge regarding the dynamic processes in the melt and their rates.…”

Section: Introductionmentioning

confidence: 99%

“…They found that when crystallization occurred under an applied uniaxial stress, nascent crystalline nuclei formed; however, their growth was suppressed. Jabbarzadeh and Tanner 20,21 performed constant-pressure, non-equilibrium molecular dynamics (NEMD) simulations of crystallization under shear and observed that steady shearing increases the crystallization rate for both C20 and C60 chains, and that pre-shearing increases the crystallization rate for C60 and longer C162 chains, but has no discernable effect for C20.…”

Section: Introductionmentioning

confidence: 99%

Molecular simulation of flow-enhanced nucleation in n-eicosane melts under steady shear and uniaxial extension

Nicholson

Rutledge

2016

The Journal of Chemical Physics

118

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Non-equilibrium molecular dynamics is used to study crystal nucleation of n-eicosane under planar shear and, for the first time, uniaxial extension. A method of analysis based on the mean first-passage time is applied to the simulation results in order to determine the effect of the applied flow field type and strain rate on the steady-state nucleation rate and a characteristic growth rate, as well as the effects on kinetic parameters associated with nucleation: the free energy barrier, critical nucleus size, and monomer attachment pre-factor. The onset of flow-enhanced nucleation (FEN) occurs at a smaller critical strain rate in extension as compared to shear. For strain rates larger than the critical rate, a rapid increase in the nucleation rate is accompanied by decreases in the free energy barrier and critical nucleus size, as well as an increase in chain extension. These observations accord with a mechanism in which FEN is caused by an increase in the driving force for crystallization due to flow-induced entropy reduction. At high applied strain rates, the free energy barrier, critical nucleus size, and degree of stretching saturate, while the monomer attachment pre-factor and degree of orientational order increase steadily. This trend is indicative of a significant diffusive contribution to the nucleation rate under intense flows that is correlated with the degree of global orientational order in a nucleating system. Both flow fields give similar results for all kinetic quantities with respect to the reduced strain rate, which we define as the ratio of the applied strain rate to the critical rate. The characteristic growth rate increases with increasing strain rate, and shows a correspondence with the nucleation rate that does not depend on the type of flow field applied. Additionally, a structural analysis of the crystalline clusters indicates that the flow field suppresses the compaction and crystalline ordering of clusters, leading to the formation of large articulated clusters under strong flow fields, and compact well-ordered clusters under weak flow fields. Published by AIP Publishing. [http://dx

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Crystallization of alkanes under quiescent and shearing conditions

Cited by 47 publications

References 29 publications

The unique properties of the solid-like confined liquid films: A large scale molecular dynamics simulation approach

The unique properties of the solid-like confined liquid films: A large scale molecular dynamics simulation approach

Crystallization of polyethylene: A molecular dynamics simulation study of the nucleation and growth mechanisms

Molecular simulation of flow-enhanced nucleation in n-eicosane melts under steady shear and uniaxial extension

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