Bulk modulus — volume relationship in alkali halides with rocksalt structure

It is shown that the bulk modulus of the alkali halides with rocksalt structure follows the simple relation B = b₀(1 — b₁f_c) V where V₀ is the unit cell volume, f_c the spectroscopically defined covalency of the chemical bond, and b₀, b₁, and n are constants having the same values for all compounds. This result is compared with the bulk modulus scaling law found for the tetrahedral semiconductors.