Pressure transitions of alkali halides and the Born-Mayer model

The Born-Mayer model with four repulsive parameters has been employed for the study of the pressure transitions in alkali halides. Satisfactory solutions can be obtained only by multiplying the van der Waals term by K, where K > 1 for most alkali halides It has been shown that the ratio of ρ2/ρ1 is equal to the structural constant, a = rii/rij The three- and two-parameter equations are thus special cases of the four-parameter equation and b2 obtained is proportional to (1 25 rl2 + 0 75 rj2)/2.