On the Fokker–Planck approximation in the kinetic equation of multicomponent classical nucleation theory

We examine the validity of Fokker-Planck equation with linear force coefficients as an approximation to kinetic nucleation in homogeneous isothermal multicomponent condensation. Starting a discrete balance governing temporal evolution distribution function ensemble droplets and reducing it (by means Taylor series expansions) differential form vicinity saddle point free energy surface, we have identified parameters whereof smallness is necessary for resulting (in droplet variables) coefficients. The "non-smallness" these results either appearance third or higher order partial derivatives its becoming non-linear functions variables, both; this would render conventional predictions inaccurate. As numerical illustration, carried out calculations condensation five binary systems various non-ideality at T=293.15 K: 1-butanol--1-hexanol, water--methanol, water--ethanol, water--1-propanol, water--1-butanol. Our suggest that under typical experimental conditions classical theory may require two-fold modification and, hence, expression steady-state rate not be adequate consistent comparison theoretical data.