8 research outputs found
Assessment of the Thermal Conductivity of BN-C Nanostructures
Chemical and structural diversity present in hexagonal boron nitride ((h-BN)
and graphene hybrid nanostructures provide new avenues for tuning various
properties for their technological applications. In this paper we investigate
the variation of thermal conductivity () of hybrid graphene/h-BN
nanostructures: stripe superlattices and BN (graphene) dots embedded in
graphene (BN) are investigated using equilibrium molecular dynamics. To
simulate these systems, we have parameterized a Tersoff type interaction
potential to reproduce the ab initio energetics of the B-C and N-C bonds for
studying the various interfaces that emerge in these hybrid nanostructures. We
demonstrate that both the details of the interface, including energetic
stability and shape, as well as the spacing of the interfaces in the material
exert strong control on the thermal conductivity of these systems. For stripe
superlattices, we find that zigzag configured interfaces produce a higher
in the direction parallel to the interface than the armchair
configuration, while the perpendicular conductivity is less prone to the
details of the interface and is limited by the of h-BN. Additionally,
the embedded dot structures, having mixed zigzag and armchair interfaces,
affects the thermal transport properties more strongly than superlattices.
Though dot radius appears to have little effect on the magnitude of reduction,
we find that dot concentration (50% yielding the greatest reduction) and
composition (embedded graphene dots showing larger reduction that h-BN dot)
have a significant effect
Assessment of phenomenological models for viscosity of liquids based on nonequilibrium atomistic simulations of copper
Caltech Asci Technical Report 104
The thermodynamic, transport and structural properties of a binary metallic glass former in solid, liquid, and glass phases were studied using molecular dynamics simulation. We used a model binary alloy system with a sufficient atomic size mismatch and observed a glass transition in a quenching process. The diffusivity and viscosity were calculated in the liquid state and the super-cooled liquid state. The smaller atom showed higher diffusivity and more configurational randomness compared to the larger atom. The viscosity increased abruptly around the glass transition temperature. The solvent/solute concentration effect on the glass transition was examined in terms of a packing fraction. We find that the glass forming ability increases with the packing fraction in the liquid state because the densely-packed material requires more time to rearrange and crystallize