AN ORIENTATIONAL INSTABILITY AND THE LIQUID-VAPOR INTERFACE OF A DIPOLAR HARD-SPHERE FLUID

Investigating the stability of the dipolar hard sphere fluid by locali zing the spinodal we found an additional instability for medium and ty pical vapor densities, an orientational instability with formation of aligned clusters. For liquid densities we find ordinary vaporization. Then we calculate the structure of the liquid-vapor interface of a dip olar hard sphere fluid in the spirit of the weighted density approxima tion (WDA) using an equation originally derived by Lovett, Mou, and Bu ff [J. Chem. Phys. 65, 570 (1976)] and Wertheim [J. Chem. Phys. 65, 23 77 (1976)]. The surface tension is evaluated on the same level of appr oximation.