DENSITY-FUNCTIONAL THEORY OF THE WATER LIQUID-VAPOR INTERFACE .2.

An improvement of our previous extended mean-field theory of the liquid-vapour interface of water is described. This revision extends the range of validity of the theory to room temperature. The current theory is improved in three aspects: (1) the effective angle-averaged pair potential is obtained by the RAM (reference-averaged Mayer) function approximation, avoiding expansion in inverse powers of temperature; (2) die soft repulsive core of the TIP4P water model pair potential is treated accurately; and (3) the anisotropic interactions are represented by a higher-order (l = 5) multipole expansion. The current theory includes no adjustable parameters; the critical temperature T(c) is found to be 609 K. Detailed calculations are given for room temperature, where molecular-dynamics simulation results are available for comparison. A more detailed representation of the orientational distribution function is reported.