Wang Wen-Chuan

A surface tension model for liquid mixtures based on the Wilson equation

A new surface tension equation based on the thermodynamic definition of surface tension and the expression of Gibbs free energy is proposed, which is different from existing ones with respect to theoretical background and formulation. By using the Wilson equation to represent the excess Gibbs free energy, a two-parameter surface tension equation is derived for liquid mixtures. The feasibility of the equation has been tested in terms of correlation for 124 binary systems and by prediction for 16 multicomponent systems at ambient temperatures with overall average absolute relative deviation (AAD) of 0.54 and 1.36%, respectively. The model parameters obtained by correlating binary surface tension at one temperature can be used to predict surface tension at other temperatures with good accuracy. It is shown that the new equation is simple in terms of calculation, accurate in correlation and prediction and is applicable to large variety of systems.

Mixing rules for hydrogen-containing systems

Abstract Three various mixing rules for vapour-liquid equilibria (VLE) calculations of hydrogen-containing systems with the Peng-Robinson equation of state were tested. A new mixing rule which contains the composition-dependent cross parameter for the covolume b is recommended for VLE description at different temperatures.

Density functional theory for molecular orientation of hard rod fluids in hard slits

A density functional theory (DFT) is used to investigate molecular orientation of hard rod fluids in a hard slit. The DFT approach combines a modified fundamental measure theory (MFMT) for excluded-volume effect with the first order thermodynamics perturbation theory for chain connectivity. In the DFT approach, the intra-molecular bonding orientation function is introduced. We consider the effects of molecular length (i.e. aspect ratio of rod) and packing fraction on the orientations of hard rod fluids and flexible chains. For the flexible chains, the chain length has no significant effect while the packing fraction shows slight effect on the molecular orientation distribution. In contrast, for the hard rod fluids, the chain length determines the molecular orientation distribution, while the packing fraction has no significant effect on the molecular orientation distribution. By making a comparison between molecular orientations of the flexible chain and the hard rod fluid, we find that the molecular stiffness distinctly affects the molecular orientation. In addition, partitioning coefficient indicates that the longer rodlike molecule is more difficult to enter the confined phase, especially at low bulk packing fractions.

Selective aggregation of membrane proteins by membrane-mediated interactions

There are different types of membrane proteins in a cellular membrane, and most of them must correctly assemble into appropriate clusters for their cellular functions. In this work, we suggest a physical mechanism for selective aggregation of different membrane proteins without specific protein-protein attraction by dissipative particle dynamics method. A membrane-mediated interaction may result in different protein clusters with ideal mixing, nonideal mixing and demixing of different types of membrane proteins, depending on the extent of the similarity of membrane deformations by those proteins.

Dimerization of Ethene Catalyzed by Acidic Zeolites

Density functional theory(DFT)was employed to investigate the dimerization of ethene over acidic zeolites with a 5T cluster model simulating zeolite.At the B3LYP/6-311+G(3df,2p)level,the activation energy was obtained with a zero point energy(ZPE)correction.It was found that the process of the dimerization of ethene can be divided into three steps:the chemical adsorption of first ethene molecule,the physical adsorption of second ethene molecule and the dimerization reaction.The reaction proceeds by ethene chemical adsorption to form the surface ethoxide and the C-C bond formation between the ethoxide and the second ethene molecule to form the butoxide product.The calculated reaction energy barriers of ethene chemical adsorption and dimerization reaction are 108 and 149 kJ·mol-1,respectively.The obtained activation barrier of β-scission of 1-butene is 217 kJ·mol-1 in the reverse reaction of ethene dimerization.

Melting Behaviour of Core-Shell Structured Ag–Rh Bimetallic Clusters

The melting behaviour of four typical core-shell structured 309-atom Ag–Rh bimetallic clusters, with decahedral and icosahedral geometric configurations, is investigated by using molecular dynamics simulation, based on the Sutton–Chen potential. The initial atomic configurations are obtained from semi-grand canonical ensemble Monte Carlo simulations. It is found that the melting point temperature Tm increases with the mole fraction of Rh in the bimetallic clusters, and Tm of Ag–Rh icosahedral clusters is higher than those of Ag–Rh decahedral clusters with the same Rh mole fraction. It is also found that the Ag atoms lie on the surface of Ag–Rh bimetallic clusters even after melting.