PHONONS IN LIQUIDS, ONSAGERS RECIPROCAL RELATIONS, AND THE HEATS OF TRANSPORT

We continue the study of liquids considered as composed by two interac ting subsystems: a population of particles, weakly bound to the sites of a disordered lattice, and a ''gas'' of phonons. The interactions am ong the material particles and the wave packets are mediated by ''ther mal radiation forces,'' a special class of inertial effects. When the liquid system is a solution, the application of a temperature or a con centration gradient breaks the symmetry of one of the two subsystems, producing an excess of phonon-solute collisions and performing work: o n the particles, at the expense of the thermal energy of the wave pack ets. The heats of transport of thermal diffusion, isothermal diffusion , and Soret equilibrium may be statistically calculated from the energ y balance of these collisions. The expressions arrived at by this appr oach are coincident with the ones obtained by nonequilibrium thermodyn amics, although for our derivation Onsager reciprocal relations are no t required. It is also argued that, within the frame of the phonon the ory, transport processes in liquids may be treated in general by means of the classical Boltzmann transport equation, applied to phonon-part icle interactions rather than to particle-particle collisions.