  A systematic study of the leading isotropic van der Waals coefficients for
the alkali-metal atom + molecule and molecule + molecule systems is presented.
Dipole moments and static and dynamic dipole polarizabilities are calculated
employing high-level quantum chemistry calculations. The dispersion, induction,
and rotational parts of the isotropic van der Waals coefficient are evaluated.
The known van der Waals coefficients are then used to derive characteristics
essential for simple models of the collisions involving the corresponding
ultracold polar molecules.
