Accurate effective potentials and virial coefficients in real fluids Part II. Pure homodiatomics and their mixtures

Abstract

The approximate nonconformal (ANC) theory recently proposed has been very successful in determining interaction potentials for the noble gases and their mixtures. The ANC theory is used here to obtain e †ective angle averaged potentials of all homodiatomic gases for which experimental second virial coefficient data are available :and The cross virial coefficients in the mixtures of homodiatomics among. themselves and with noble gases are predicted with excellent agreement with experiment for the heavier classical gases. The atomÈatom interactions, which should be an improvement over previous results, are also determined and shown to behave regularly with atomic number. The critical temperatures and volumes of these gases vary smoothly when scaled with the parameters of the ANC potential.

Interaction potentials and thermodynamics of small polar molecules. The case of C1-Freons (halomethanes)

“…The potentials thus generated for more than 40 substances give second virial coefficients B(T ) that agree with experimental data within their precision. We have reported successful application of the theory to substances of increasing molecular complexity, starting with the noble gases [13], followed by homo-diatomic substances [14], the homologous n-alkanes and perfluoro-n-alkanes, and some hetero-diatomic and small polyatomic substances [15]. For argon, krypton and xenon the ANC potentials are very close to the best pair potentials derived by other means [13,16].…”

“…This approach leads us to construct effective potential models for substances whose experimental B(T ) data is of insufficient accuracy, or over too narrow ranges of temperature, to generate directly u ef (r). Thus, for instance, from molecular interactions (such as those of O 2 and N 2 ) it has been possible to obtain atomatom interactions (N-N and O-O in this instance) that lead to predictions of the interactions in new compounds (as of NO monomers) [14]. Also, knowledge of the influence of elongation on the effective potential of chain molecules (n-alkanes and perfluoro-alkanes) leads to predictions of the potentials (and the properties) of longer molecules for which experimental information is unavailable, scarce or of indifferent precision [15].…”

Effective intermolecular potentials in theoretical thermodynamics of pure substances and solutions

“…(6) with high degree of approximation. These substances include: the noble gases (He, Ne, Ar, Kr, Xe, Rn) [15], homodiatomic molecules (H 2 , D 2 , N 2 , O 2 , F 2 , Cl 2 ) [27], alkanes (up to C 8 ) and perfluoroalkanes (up to C 7 ) [28], linear (CO 2 , C 2 H 4 ), small dipolar molecules (H 2 O, D 2 O, NH 3 , HCl, NO, CO), hexadecapolar (SF 6 ) [29] and the C 1 -Freons [30]. Indeed, since the potential defined in (5) is constructed especially to satisfy (6), it is no surprise that the results of the one-s ANC model from B exp (T) data are within estimated experimental error.…”

“…These substances are: three noble gases (Ar, Kr and Xe), two diatomics (N 2 and O 2 ) and three light alkanes (CH 4 , C 2 H 6 , C 3 H 8 ). The ANC parameters ε 0 , δ 0 and s were obtained from inversion of B exp (T) data [15,27,28] and ν taken from quantum semi-empirical techniques [3,32], inversion of acoustic properties [12,33] or direct evaluation [34]. For the purpose of this paper we only need to consider a concrete example of the calculation of C(T).…”

Effective Intermolecular Interaction Potentials of Gaseous Fluorine, Chlorine, Bromine, and Iodine

“…Whereas the calculations of Bohn et al [9] for Cl 2 are not in good agreement with the experimental results of Morrison at low temperatures [10], more recent studies of Meng and Duan [11] compare favorably well with experiments. Rio and co-authors used the approximate nonconformal theory [12] to obtain the effective interaction potentials for a lot of gases, including F 2 and Cl 2 . Their results are in reasonably good agreement with experimental data [13].…”