Attractive interaction potentials and the binary collision approximation

The binary collision approximation (BCA) is applied to interatomic potentials with an attractive region surrounding a repulsive core. The evaluation of the collision apsis is modified and the time integral is reformulated. A new program, TABULA, was developed to study different formulations of the BCA and methods of numerical quadrature and to tabulate the scattering integrals and related quantities. TABULA is illustrated by calculations for Moliere and Morse potentials. These show the new time integral equation to be more accurate than the older one. The modifed BCA was installed in a new version of MARLOWE. The increased accuracy reduces the lengths of replacement sequences. Attractive potentials are illustrated by cascade calculations in Au with similar Moliere and Morse potentials. The results show systematic differences related to differences in the potentials and in the kinematics of collisions.