Entropy-driven structure and dynamics in carbon nanocrystallites

McNutt, Nicholas W.; Wang, Qifei; Rios, Orlando; Keffer, David J.

doi:10.1007/s11051-014-2365-7

Cited by 10 publications

(18 citation statements)

References 46 publications

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“…With regard to the behavior of the PDF in the region that contains the d spacing, a clear relation between the nature of the curve in this region and the d-spacing width must be understood. This d-spacing distance was directly calculated for the crystallites within the equilibrated composite systems using the procedure reported by McNutt et al (2014). Only crystallites that remained intact through the process of equilibration were considered for this measurement.…”

Section: Direct Measurement Of D Spacingmentioning

confidence: 99%

“…The importance of the d-spacing measurements is to characterize not the exact values of d spacing but rather the trends in d-spacing changes as parameters vary so that the same trends can be understood for the experimental composites. Two geometric measures of d spacing between adjacent planes in a crystallite were considered: breathing distance and centerof-mass (COM) distance, as previously used (McNutt et al, 2014). The COM distance is defined to be the length of the Molecular representation of three composite systems before equilibration (top row) and after (bottom row): (a) and (d) r = 5 Å , = 1.94 g cm À3 , È c = 0.9; (b) and (e) r = 7 Å , = 1.51 g cm À3 , È c = 0.5; (c) and ( f ) r = 17 Å , = 1.38 g cm À3 , È c = 0.1.…”

Section: Direct Measurement Of D Spacingmentioning

confidence: 99%

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Structural analysis of lignin-derived carbon composite anodes

et al. 2014

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The development of novel lignin‐based carbon composite anodes consisting of nanocrystalline and amorphous domains motivates the understanding of the relationship of the structural properties characterizing these materials, such as crystallite size, intracrystallite d spacing, crystalline volume fraction and composite density, with their pair distribution functions (PDFs), obtained from both molecular dynamics simulation and neutron scattering. A model for these composite materials is developed as a function of experimentally measurable parameters and realized in 15 composite systems, three of which directly match all parameters of their experimental counterparts. The accurate reproduction of the experimental PDFs using the model systems validates the model. The decomposition of the simulated PDFs provides an understanding of each feature in the PDF and allows for the development of a mapping between the defining characteristics of the PDF and the material properties of interest.

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Section: Direct Measurement Of D Spacingmentioning

confidence: 99%

Section: Direct Measurement Of D Spacingmentioning

confidence: 99%

Structural analysis of lignin-derived carbon composite anodes

et al. 2014

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“…However, at room temperature, the peak due to this planar spacing is broadly distributed, which is why graphitic nanoparticles have been called entropically driven structures. 16 This feature can be lost in the background of the total RDF, a point that highlights the value of this decomposition.…”

Section: Crystalline-crystalline Intercrystallite (Ccinterc) Componentmentioning

confidence: 97%

“…Here we used 3 Å , a reasonable value supported by experiment. 16 A nanocrystallite of radius 5 Å contains three planes. Therefore, there will be contributions to the RDF at two distances: adjacent planes and planes separated by one plane between them.…”

Section: Crystalline-crystalline Intercrystallite (Ccinterc) Componentmentioning

confidence: 99%

Hierarchical Model for the Analysis of Scattering Data of Complex Materials

Oyedele

McNutt

Rios

et al. 2016

JOM

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Interpreting the results of scattering data for complex materials with a hierarchical structure in which at least one phase is amorphous presents a significant challenge. Often the interpretation relies on the use of large-scale molecular dynamics (MD) simulations, in which a structure is hypothesized and from which a radial distribution function (RDF) can be extracted and directly compared against an experimental RDF. This computationally intensive approach presents a bottleneck in the efficient characterization of the atomic structure of new materials. Here, we propose and demonstrate an approach for a hierarchical decomposition of the RDF in which MD simulations are replaced by a combination of tractable models and theory at the atomic scale and the mesoscale, which when combined yield the RDF. We apply the procedure to a carbon composite, in which graphitic nanocrystallites are distributed in an amorphous domain. We compare the model with the RDF from both MD simulation and neutron scattering data. This procedure is applicable for understanding the fundamental processing-structure-property relationships in complex magnetic materials.

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“…A higher temperature leads to a higher rate of transport of thermal phonons [32]. These phonons are associated with lesser frequencies i.e., the transport moves to the ballistic regime with higher wavelengths [39]. This results in an easier thermal transport and consequently a lower heat capacity at higher temperatures.…”

Section: Effect Of Temperature On Heat Capacitymentioning

confidence: 99%

Enhanced Specific Heat Capacity of Liquid Entrapped between Two Solid Walls Separated by a Nanogap

2020

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Size and thermal effect on molar heat capacity of liquid at constant volume (Cv) on a nanometer scale have been investigated by controlling the temperature and density of the liquid domain using equilibrium molecular dynamics (EMD) simulations. Lennard-Jones (LJ) type molecular model with confinement gap thickness (h) 0.585 nm to 27.8 nm has been used with the temperature (T) ranging from 100 K to 140 K. The simulation results revealed that the heat capacity of the nanoconfined liquid surpasses that of the bulk liquid within a defined interval of gap thickness; that the temperature at which maximum heat capacity occurs for a nanoconfined liquid vary with gap thickness following a power law, TCv,max = 193.4 × (h/a)−0.3431, ‘a’ being the lattice constant of Argon (solid) at 300 K; and that for a specified gap thickness and temperature, the confined liquid can exhibit a heat capacity that can be more than twice the heat capacity of the bulk liquid. The increase in heat capacity is underpinned by an increase in non-configurational (phonon and anharmonic modes of vibration) and configurational (non-uniform density distribution, enhanced thermal resistance, guided molecular mobility, etc.) contributions.

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Entropy-driven structure and dynamics in carbon nanocrystallites

Cited by 10 publications

References 46 publications

Structural analysis of lignin-derived carbon composite anodes

Structural analysis of lignin-derived carbon composite anodes

Hierarchical Model for the Analysis of Scattering Data of Complex Materials

Enhanced Specific Heat Capacity of Liquid Entrapped between Two Solid Walls Separated by a Nanogap

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