A molecular dynamics simulation study of octopoles in the field of a planar surface

Odd–even effects in the homologous series of alkyl-cyanobiphenyl liquid crystals: A molecular dynamic study

For the first five members of the homologous series of 4-n-alkyl-4'-cyanobiphenyls in the nematic and isotropic phases, molecular dynamics (MD) simulations were performed by using a united atom model. An odd-even effect was seen to be found in the molecular length, width, biaxiality, and inertia tensor anisotropy with the length of alkyl chain. The distributions of the molecular length, width, and inertia tensor anisotropy were presented. The orientational distributions of the last C--C bonds in the alkyl chain were also evaluated for nematic and isotropic phases.

Prediction of viscosity for molecular fluids at experimentally accessible shear rates using the transient time correlation function formalism

Nonequilibrium molecular dynamics (NEMD) simulations were performed and the transient time correlation function (TTCF) method applied to calculate the shear viscosity of n-decane. Using the TTCF method we were able to calculate the viscosity at shear rate orders of magnitude lower than is possible by direct NEMD simulation alone. For the first time for a molecular fluid, we were able to simulate shear rates accessible by experimental measurements, which are typically performed at shear rates well below those accessible by NEMD simulation. The TTCF method allows us to close the gap between the lowest shear rates accessible by MD simulation and the highest shear rates possible in experimental studies. Additionally a multiple time step method for Gaussian thermostatted SLLOD equations of motion was developed following earlier work [G. A. Pan et al., J. Chem. Phys. 122, 4114 (2005)] for atomic fluids.

Topological defects in schlieren textures of biaxial and uniaxial nematics

Monte Carlo and theoretical studies of thin 3D films of biaxial and uniaxial nematics with tangential boundary conditions show distinct differences in structure and evolution of topological defects. In the uniaxial films, defects of strength k=+/-1 are point defects that bear no bulk singularity and disappear by annihilation with each other. In the biaxial films, k=+/-1 defects are true singular bulk disclinations that split into pairs of k=+/-1/2 lines; the latter disappear by annihilation processes of the type +1/2-1/2=0. These observed differences are of relevance for the current debate on the existence of biaxial phases.