Heat capacity of the halogen-bridged mixed-valence complex Pt2(dta)4I (dta) CH3CS2-) has been measured in the temperature region between 6 and 386 K. The complex exhibited a phase transition of order-disorder type at Ttrs) 373.4 K, from being arranged in an ordered helical form of four dta ligand planes around the central Pt-Pt axis to dynamically jumping between two orientations. Neither latent heat nor distinct thermal hysteresis was observed for the phase transition, suggesting that the phase transition is of higher-order rather than of first-order. The transition enthalpy and entropy were determined to be

The density profiles and the diffusion behavior of fluid argon confined in micropores were studied by molecular-dynamics simulations. The effects of pore size width!, temperature and number density on the density profiles and the self-diffusion coefficients in micropores were simulated with pore widths from 0.6 to 4.0 nm. The density profiles are greatly affected by the pore size. Strong inhomogeneities in the channel direction and vapor-liquid phase separation in the micropores were observed when initial conditions were chosen in the coexistence region of the fluid. The self-diffusion coefficient in the channel direction in the pores was found to be much lower than in the bulk, and decreasing with decreasing pore size, decreasing temperature, and increasing density.

A new stainless steel apparatus for measuring azeotropic points of binary as well as multicomponent systems at elevated pressures has been developed. The azeotropic temperatures and compositions of six binary systems composed of cyclohexane, 2-propanol, ethyl acetate, and butanone were determined at elevated pressures, correlated by empirical equations with pressure, and predicted by the UNIFAC group contribution method. The calculations demonstrate that the correlated data are in good agreement with experimental values.

The adsorption equilibria of ternary and quaternary mixtures of short linear alkanes, involving methane, ethane, propane, and n-butane, were simulated by using the configurational-bias Monte Carlo technique in grand canonical ensemble in MFI zeolite. The simulation results are in good agreement with the experimental data. The adsorption isotherms in MFI zeolite show that the longer chain component is preferentially adsorbed at low pressures. Its adsorption increases and then decreases as the pressure increases. But the shorter chain component is adsorbed at higher pressures and its adsorption increases as the pressure increases. The selectivity of ISV and MFI is much higher than that of MOR. The selectivity increases rapidly as the mole fraction of methane in the gas phase increases, but the change of selectivity of MOR is not obvious in an methane-ethane-propane mixture. The adsorbed amount in mixtures is in the order of ISV>MFI>MOR.

The self-diffusion coefficients were calculated by molecular dynamics simulations and the effects of pore width, temperature, and fluid density on diffusion behavior of simple fluid argon and polar fluid water confined in micropores were analyzed and studied.Amathematical model describing diffusion behavior of fluids confined in micropores was proposed from the theories of molecular dynamics and molecular kinematics, and validated on the basis of the simulation results at various conditions. The model indicates that the diffusion coefficient is proportional to the square root of the pore width and to the temperature divided by the density squared. It is applicable to either liquid or gas states and only two parameters are required.