The temperature-dependent mass diffusion coefficient is computed using transition state theory. Ab initio supercell phonon calculations of the entire system provide the attempt frequency, the activation enthalpy, and the activation entropy as a function of temperature. Effects due to thermal lattice expansion are included and found to be significant. Numerical results for the case of hydrogen in nickel demonstrate a strong temperature dependence of the migration enthalpy and entropy. Trapping in local minima along the diffusion path has a pronounced effect especially at low temperatures. The computed diffusion coefficients with and without trapping bracket the available experimental values over the entire temperature range between 0 and 1400 K.

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Murphree vapor point efficiencies were determined for the systems n-hexane-methylcyclopentane, nhexane-methylcyclopentane-ethanol, and n-hexane-methylcyclopentane-ethanol-benzene. The results obtained on the binary system are in agreement with efficiencies calculated by the AlChE correlation. For the ternary, surface-tension negative systems had higher efficiencies than positive ones, as expected for operations in the spray regime. A mathematical model was developed for the prediction of efficiencies in the systems investigated. The work on the multicomponent systems confirms the concept that the efficiencies of all components may not be equal. In all cases, the major resistance to mass transfer was in the vapor phase. The data were obtained in a sieve tray column of 1 V/s-in. diam.

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