Reference tables of second pVT-virial coefficients B(T), viscosity η(T), and self-diffusion ρD(T) are given for all neat alkanes CnH2n+2, n<6, for temperatures T⩽1200 K starting at 100 K for CH4, 150 K for C2H6, and 180 K for C3H8, n-C4H10, i-C4H10, n-C5H12, i-C5H12, and C(CH3)4. Restricting ourselves to low densities the thermophysical properties are calculated by means of an isotropic (n-6) Lennard-Jones temperature dependent potential (LJTDP). In this model the potential well depth εeff(T) and the separation at minimum energy Rm(eff)(T) are explicitly temperature dependent, whereas the repulsive term n>12 is independent of T. The LJTDP has been used before in order to construct reference tables of thermophysical properties of neat gases [Zarkova and Hohm, J. Phys. Chem. Ref. Data 31, 183 (2002)] and binary mixtures [Zarkova, Hohm, and Damyanova, J. Phys. Chem. Ref. Data 32, 1591 (2003)]. However, those studies were restricted to atoms and globularly shaped nondipolar molecules. Here the approach is extended to elongated, not necessarily spherically symmetric, and in part slightly dipolar molecules. As in previous works the potential parameters εeff(T), Rm(eff)(T), and n are determined by minimizing the root-mean-square deviation between calculated and experimentally obtained thermophysical properties B(T), η(T), ρD(T), and the second acoustic virial coefficient β(T) normalized to their experimental error. In extension of our previous efforts we present a thorough statistical analysis of the experimental input data which gives us the possibility to select primary data which could be used to build up a database.

Self-consistent calculations of interaction pVT-virial coefficients B 12 (T ), viscosities η mix (T ), and diffusion coefficients D 12 (T ) of binary mixtures of the alkanes C n H 2n+2 (n < 6) are presented. This study is based on the recently developed model of the (n-6) Lennard-Jones temperature-dependent potential (LJTDP) and uses already obtained potential parameters of the pure alkanes as input data. The well-known and simple Lorentz-Berthelot (LB) and the more elaborate Tang-Toennies (TT) mixing rules are applied to the potential parameters of the pure alkanes in order to determine those of the mixtures. The new Hohm-Zarkova-Damyanova (HZD) mixing rule, which is an extension of the TT-mixing rule, is also considered. The HZD takes into account that for the LJTDP model, in general, the repulsive parameter is an independent variable whose value n = 12. As in a recent examination of binary mixtures of globular molecules, the LB-mixing rule is superior to TT-and HZD-mixing rules when calculating equilibrium properties such as B 12 (T ). For the transport properties η mix (T ) and D 12 (T ), the new mixing rule performs slightly better.

In this paper the isotropic temperature-dependent potential (ITDP) approach and the concepts introduced in our previous papers have been used to calculate equilibrium and transport properties of low-density gas mixtures. The twelve binary mixtures considered here are: Ar-CH 4 , Ar-CF 4 , Ar-SF 6 , Ar-C(CH 3 ) 4 , Kr-CH 4 , Kr-CF 4 , Kr-SF 6 , Kr-C(CH 3 ) 4 , Xe-CH 4 , Xe-CF 4 , Xe-SF 6 and Xe-C(CH 3 ) 4 . The (n − 6) Lennard-Jones potential parameters n (repulsive parameter), R m (equilibrium distance), and ε (potential well depth) of the pure noble gases Ar, Kr, and Xe are obtained by a minimization of the sum of squared deviations between experimental and calculated viscosity (η), and second pVT (B) and acoustic (β) virial coefficients normalized to their relative experimental error a exp . The number of included experimental points for B, β, η was N = 305, 210, and 167 for Ar, Kr, and Xe, respectively. For the pure globular gases the potential parameters were taken from previous publications. The calculations of B, η, and ρD 12 of binary mixtures were compared with experimental data by using two different mixing rules (Lorentz-Berthelot and Tang-Toennies). Recommended sets and fitting formulae for the potential parameters that can be used for the calculation of low-pressure thermophysical properties of these mixtures are provided.

This work presents results of an extension of our earlier studies of the transport and equilibrium properties of pure heavy globular gases. It demonstrates a simple and reliable procedure for estimating the equilibrium and transport properties of their mixtures using the pure gas potentials of interaction when there are no available experimental data. Here we consider binary gas mixtures of globular gases between themselves and with the noble gases as well. The gases involved are: BF3, CH4, CF4, SiF4, SiCl4, CCl4, SF6, MoF6, WF6, UF6, C(CH3)4, Si(CH3)4, Ar, Kr, and Xe. The calculations were performed by means of the so called isotropic temperature–dependent potential (ITDP) introduced by us earlier and applied to some binary mixtures (CH4–CF4, CH4–SF6, CF4–SF6). The CH4–CH4 and noble gases potentials of interactions have been determined in a (n−6) Lennard-Jones shape in the temperature range 200–1000 K by fitting a large number of viscosity and pVT–second virial coefficient data measured by different authors with different experimental techniques. The ITDP parameters of molecular gases were taken from the tables we have determined and published earlier [L. Zarkova and U. Hohm, J. Phys. Chem. Ref. Data 31, 183 (2002)]. Simple combination rules allow us to take into account the influence of the temperature on the thermophysical properties of the binary gas mixtures containing heavy globular molecules. Tables with potential parameters of equal and unequal particles and properties of the equimolar mixtures are given for all mixtures in the temperature range 200–900 (1000) K. The deviations between experimental and calculated viscosity and second virial coefficient data of some more examined mixtures permit to evaluate the quality of the proposed approach.