58 research outputs found
M3B: A Coarse Grain Force Field for Molecular Simulations of Malto-Oligosaccharides and Their Water Mixtures
Anomalous Heat Conduction and Anomalous Diffusion in Low Dimensional Nanoscale Systems
Thermal transport is an important energy transfer process in nature. Phonon
is the major energy carrier for heat in semiconductor and dielectric materials.
In analogy to Ohm's law for electrical conductivity, Fourier's law is a
fundamental rule of heat transfer in solids. It states that the thermal
conductivity is independent of sample scale and geometry. Although Fourier's
law has received great success in describing macroscopic thermal transport in
the past two hundreds years, its validity in low dimensional systems is still
an open question. Here we give a brief review of the recent developments in
experimental, theoretical and numerical studies of heat transport in low
dimensional systems, include lattice models, nanowires, nanotubes and
graphenes. We will demonstrate that the phonon transports in low dimensional
systems super-diffusively, which leads to a size dependent thermal
conductivity. In other words, Fourier's law is breakdown in low dimensional
structures
Effect of Covalent Functionalisation on Thermal Transport Across Graphene-Polymer Interfaces
This paper is concerned with the interfacial thermal resistance for polymer
composites reinforced by various covalently functionalised graphene. By using
molecular dynamics simulations, the obtained results show that the covalent
functionalisation in graphene plays a significant role in reducing the
graphene-paraffin interfacial thermal resistance. This reduction is dependent
on the coverage and type of functional groups. Among the various functional
groups, butyl is found to be the most effective in reducing the interfacial
thermal resistance, followed by methyl, phenyl and formyl. The other functional
groups under consideration such as carboxyl, hydroxyl and amines are found to
produce negligible reduction in the interfacial thermal resistance. For
multilayer graphene with a layer number up to four, the interfacial thermal
resistance is insensitive to the layer number. The effects of the different
functional groups and the layer number on the interfacial thermal resistance
are also elaborated using the vibrational density of states of the graphene and
the paraffin matrix. The present findings provide useful guidelines in the
application of functionalised graphene for practical thermal management.Comment: 8 figure
Gas Sorption and Barrier Properties of Polymeric Membranes from Molecular Dynamics and Monte Carlo Simulations
Chain and local dynamics of polyisoprene as probed by experiments and computer simulations
The dynamics of designed short polyisoprene (PI) chains in the melt is investigated on a wide temperature window using dielectric relaxation spectroscopy and pulsed field gradient nuclear magnetic resonance (NMR). At high temperatures, molecular dynamics (MD) simulations performed using two different models (an explicit atom model and a united atom one) capture very well the dynamic properties documented experimentally. Structures pre-equilibrated with end-bridging Monte Carlo are used as initial configurations for MD runs at different temperatures, providing predictions for the temperature dependence of the dynamics of this bulk PI. Local dynamics is unique, independently of the probe (dielectric relaxation, dynamic light scattering, nuclear magnetic resonance, neutron scattering), although mean correlation times are significantly affected, to different extents, by librations. Chain dynamics over the molecular weight and temperature range studied can be described well by the Rouse model, as shown by both experimental data and a normal mode analysis on simulation trajectories. Deviations from the Rouse model emerge for the high modes at short times; still, this model offers a rather accurate picture. (C) 2003 American Institute of Physics
Do Inverse Monte Carlo Algorithms Yield Thermodynamically Consistent Interaction Potentials?
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