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Then, the bands of the semiconductor particle become flat, and the flat-band condition will be established.Since the electrochemical potential of photogenerated holes is still very high at the flat-band condition, the holes more or less react with reductants faster than electrons even in the flat-band condition. Here we consider the case where further charge separation occurs from the semiconductor particle to the bulk of the solution. In such a case, true charge (electrons) further accumulate on the semiconductor particle, and, most possibly, the potential drop across the Helmholtz layer is changed to shift the band edges to the more negative, holding the bands flat. The particle potential will come into a steady state when ve = vh. If, on the contrary, another case occurs where a strong accumulation layer is formed in the semiconductor particle by holding the band edges pinned, the value of Vp still has meaning since, in any case, Vp represents the pseudo-Fermi level of electrons of the semiconductor particle under illumination.

Combination rules for intermolecular potential parameters based on different approximations for the long-range dispersion energy are derived and applied to the Lennard-Jones (12–6) and Kihara potential functions. The resulting group of rules is given by the expressions σ12 = <σ≳j, and ε12 = <εσ6γ≳i/‖<σ≳6j<γ≳k ‖, where the i,j, and k subscripts may adopt the values a, g, or h indicating the type of mean (arithmetic, geometric, or harmonic, respectively) to be taken for the magnitude within the brackets. Expressions for γ depend on the approximation chosen for the van der Waals coefficient c6. This group of rules includes most of those previously proposed and others which are new. Experimental values of the interaction virial coefficient and unlike-pair potential parameters obtained from viscosity data are used to test the validity of the rules. Six related rules are shown to be satisfactory for both potential functions and for accurate correlation of virial and viscosity data as well.