Virial term, diffusion

Thus one must rely on macroscopic theories and empirical adjustments for the determination of potentials of mean force. Such empirical adjustments use free energy data as solubilities, partition coefficients, virial coefficients, phase diagrams, etc., while the frictional terms are derived from diffusion coefficients and macroscopic theories for hydrodynamic interactions. In this whole field of enquiry progress is slow and much work (and thought ) will be needed in the future. 

The viscosity, thermal conductivity and diffusion coefficient of a monatomic gas at low pressure depend only on the pair potential but through a more involved sequence of integrations than the second virial coefficient. The transport properties can be expressed in terms of collision integrals defined [111] by... 

Phillies (76,77) has subsequently discussed the empirical extension of this classical diffusion theory to higher terms in the virial expansions. Recently, Batchelor has carried out a more detailed analysis of the intermolecular hydrodynamic interactions contributing to kf and arrived at the conclusion (78) ... 

Hellmann et al. [23, 177,178] have proposed ab initio force fields for several small molecules, such as helium, neon, or methane, based on the Tang and Toennies potential (9) and coulombic terms (14). With these force fields, gas phase properties like second virial coefficient, shear viscosity, thermal conductivity, or self-diffusion coefficient can be predicted extremely accurately. Typically, the generated data are within the experimental uncertainty. 

B van Deemter eqnation molecular diffusion term second virial... 

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