AbstractThe third order elastic constants and the pressure derivatives of second order elastic constants of ternary zinc blende semiconductor, CuGe2P3are analysed using two theoretical approaches. The first model consists of Born‐Mayer type short‐range potential in addition to the long range many‐body interaction and Coulomb potentials, while the second model is derived from Martin's bond‐bending and stretching force model. It is shown that although the bond bending force model gives a reasonably good fitting to these properties, the present model including three body forces explains adequately the features of the anharmonic behaviour reasonab