Ming-Liang Liao

Deformation behaviors of an armchair boron-nitride nanotube under axial tensile strains

Deformation behaviors of an (8,8) boron-nitride nanotube (BNNT) under axial tensile strains were investigated via molecular dynamics (MD) simulations. The Tersoff potential was employed in the simulations with potential parameters determined by fitting the MD simulations results to those obtained from density functional theory calculations for BNNTs with the aid of the force-matching method. Variations in the axial stress, bond lengths, bond angles, radial buckling, and slip vectors with tensile strain were all examined. The axial, the radial, and tangential components of the slip vector were employed to monitor the local elongation, the local necking, and the local twisting deformations, respectively, near the tensile failure of the BNNT. From this study, it was noted that the BNNT started to fail at the failure strain of 26.7%. The components of the slip vector grew abruptly and rapidly after the failure strain, especially for the axial component. This implies that the local elongation dominates the ten...

Hydrogen-bond dynamics of interior and surface molecules in a water nanocluster: temperature and size effects

Molecular dynamics simulations are employed to investigate the effects of temperature and size on the hydrogen-bond dynamics of interior molecules and surface molecules in a water nanocluster. The flexible three-centred (F3C) water model is invoked in the simulations. To inspect the dynamics of the interior hydrogen bonds and the surface hydrogen bonds, a spherical water nanocluster is modelled and then divided into interior molecules and surface molecules according to the density profile of the water nanocluster. It is observed that at higher temperatures the average number of hydrogen bonds decreases and yields faster hydrogen-bond relaxation for both interior molecules and surface molecules of the water nanocluster. Furthermore, the surface molecules have a lower average number of hydrogen bonds than the interior molecules. The lifetime of the surface hydrogen bonds is slightly longer than that of the interior hydrogen bonds, whereas the hydrogen-bond structural relaxation time of the surface molecules is more obviously slower than that of the interior molecules. Regarding the size effect, a larger water nanocluster is seen to have a larger average number of hydrogen bonds and a longer hydrogen-bond structural relaxation time.

Size and chain length effects on structural behaviors of biphenylcyclohexane-based liquid crystal nanoclusters by a coarse-grained model

Size and chain length effects on structural behaviors of liquid crystal nanoclusters were examined by a coarse-grained model and the configurational-bias Monte Carlo (CBMC) simulation. The nanoclusters investigated in this study are composed of the biphenylcyclohexane-based BCH5H liquid crystal molecule and its derivatives. Results of the study show that the average energy decreases (i.e., more negative) as the cluster size (i.e., the number of molecules) increases. With the increasing cluster size, the equilibrium conformation of the nanocluster changes gradually from a pipe-like structure (for the smaller systems) to a ball-like cluster (for the larger systems). The order parameter of the system reduces with the transition of the equilibrium conformation. Regarding the chain length effect, the pipe-like equilibrium conformation (for the smaller systems) was observed more close to a pipe as the length of the tail alkyl chain of the derivatives extended. However, due to the flexibility of the tail alkyl chain, the pipe conformation of the system deflects slightly about its cyclohexyl group as the tail extends further.

Conformations of PMMA Thin Films on an Au (111) Substrate: Chain-Length and Tacticity Effects

Chain-length and tacticity effects on conformations of poly(methyl methacrylate) (PMMA) thin films on an Au (111) substrate at room temperature were investigated by means of molecular dynamics (MD) simulations. The MMA oligomers were found to exhibit a flattened conformation parallel to the Au substrate in the contact region and a little flattened conformation in the surface region for both the short-chain and the long-chain thin films. The flattened conformation remains in the bulk region for the long-chain case, but it is not present in the bulk region of the short-chain film.

Rheological Properties of Water Films Nanoconfined in Parallel Au Plates by Molecular Dynamics Simulations

Rheological properties of water films nanoconfined in two parallel Au plates are investigated with the aid of molecular dynamics simulations. The density distribution, velocity profile, and diffusion coefficients of the water film in a Couette flow are studied. Shear viscosity and its dependence on the shear rate of the water film are also examined in the present research. It is found that the density of the water molecules near the plates is much higher than that in the other regions. This indicates that many water molecules are adsorbed by the plates and adsorbed layers are formed in the vicinity of the plates. The diffusion of the whole film increases dramatically as the shear rate becomes greater than 1010 s-1. The shear viscosity decreases as the shear rate increases, especially for the water film with a small thickness, which indicates the shear-thinning behavior for viscosity of the nanoconfined film. Moreover, an increase in shear viscosity with a decrease in the film thickness can also be found in the present study.

Investigation into Temperature and Size Effects on Behavior of Nano-scale Water Clusters

Temperature and size effects on behavior of nano-scale water clusters are investigated by means of molecular dynamics simulations. Hydrogen bond properties and the dipole moment of the water clusters are examined in order to explore the effects of temperature and cluster size on the behaviors of the clusters. The flexible three-centered (F3C) water potential is used to model the inter- and intra-actions of the water molecule. It is found that as the temperature rises, the average number of hydrogen bonds per water molecule decreases, while the average length of the hydrogen bond increases. Moreover, with a rise in temperature, the average dipole moment per water molecule will slightly decrease. The effect of cluster size, however, is less significant on the hydrogen bond properties and the dipole moment