Molecular dynamics of small alkanes in an external force field

Weber, Thomas A.; Annan, Nancy D.

doi:10.1080/00268978200101191

Cited by 14 publications

(2 citation statements)

References 9 publications

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“…By molecular simulation (most commonly nonequilibrium molecular dynamics), the behavior of molecules under shear has been explored. It is reported − that molecules tend to align with the flow direction as the shear rate increases. For atoms and small molecules, very high shear rates (>10 10 s –1 ) are required to cause a prominent alignment.…”

Section: Introductionmentioning

confidence: 99%

Influence of Agitation and Fluid Shear on Primary Nucleation in Solution

Liu

Rasmuson

2013

Crystal Growth & Design

159

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The influence of mechanical energy on primary nucleation of butyl paraben has been investigated through 1320 cooling crystallization experiments. The induction time has been measured at different supersaturations, temperatures, and levels of mechanical energy input, in two different flow systems. There is an overall tendency in the experiments that primary nucleation is promoted by increased input of mechanical energy. In small vials agitated by magnetic stir bars, the induction time was found to decrease with increasing agitation power input raised to 0.2 in the low agitation region. However, further increase in agitation leads to an increase again in the induction time. In a concentric cylinder apparatus of Taylor−Couette flow type, the induction time is inversely related to the shear rate. By fitting the parameters of the classical nucleation theory to experimental data, it is shown that the results can be explained as an influence on the pre-exponential factor. The treatment behind the pre-exponential factor is extended to account for the contribution of forced convection in a solution exposed to agitation and fluid shear. However, the analysis cannot verify that increased rate of mass transfer can explain the results. Alternative mechanisms are discussed based on a comprehensive review of the relevant literature. Shear-induced molecular alignment and in particular agitation-enhanced cluster aggregation are mechanisms that appear to deserve further attention. ■ INTRODUCTIONCrystallization processes are of significant importance to our society in industrial production of metallurgic and polymeric materials, and of inorganic and organic compounds; in the formation of shells and bone structures in nature; and in diseases such as the appearance of kidney stones and precipitates of amyloid proteins. In the industrial production of pharmaceutical compounds, crystallization is repeatedly used to separate and purify intermediates and is of major importance for the purification of the final product. Primary nucleation denotes the formation of a new particle in the solution, having a size sufficient for it to be thermodynamically stable at the prevailing conditions. Crystal nucleation has a governing influence on product properties and robustness of the process but is the mechanism of crystallization that is the least understood. This leads to significant problems in the design, operation, and control of industrial processes. Nucleation behavior is known to be unreliable and case sensitive. Because of this, industrial processes are developed by trial and error, and they often lack sufficient robustness. Sometimes lack of reproducibility requires rework or even disposal of the batch. The slow development of the fundamental understanding of primary nucleation is due to the nanoscale size range, the very strong nonlinear dependence on the supersaturation, and the significant stochastic component.The earliest evidence on the effect of mechanical stimulus on primary nucleation can be traced to the beginning of the 20th cent...

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Section: Introductionmentioning

confidence: 99%

Influence of Agitation and Fluid Shear on Primary Nucleation in Solution

Liu

Rasmuson

2013

Crystal Growth & Design

159

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“…The idea of introducing an external force field in the molecular dynamics simulations of polymeric materials is not new. For example, Weber and Annan 20 introduced external compression and shearing forces in their adiabatic…”

Section: Magnetic Field and Molecular Dynamicsmentioning

confidence: 99%

Adhesion Energy of Single-Wall Carbon Nanotube-Polyethylene Composite: Effect of Magnetic Field

Al-Haik¹,

Hussaini²

2006

j comput theor nanosci

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In this paper, we investigate the adhesion energy at the interface between single-wall carbon nanotubes (SWCNT) and polyethylene matrixwith and without an external magnetic field. The carbon nanotubes are of two different chiralities—armchair (10, 10), and zigzag (10, 0), and the external high magnetic field is of 25 Tesla intensity. The study employs molecular dynamics simulations and concludes that the magnetic field decreases the interfacial adhesion energy although it increases the individual potential energies of the nanotubes, polyethylene, and composite.

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The rheological properties of model liquid n-hexane determined by non-equilibrium molecular dynamics

Brown

Clarke

1983

Chemical Physics Letters

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Molecular dynamics of small alkanes in an external force field

Cited by 14 publications

References 9 publications

Influence of Agitation and Fluid Shear on Primary Nucleation in Solution

Influence of Agitation and Fluid Shear on Primary Nucleation in Solution

Adhesion Energy of Single-Wall Carbon Nanotube-Polyethylene Composite: Effect of Magnetic Field

The rheological properties of model liquid n-hexane determined by non-equilibrium molecular dynamics

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