Form factors directly determined from momentum space Hartree-Fock solutions: H-2 and Li-2

The characteristics of the theoretical form factors computed from momentum space wave functions of quantum chemistry (i.e., vectorial quantities including appropriate phase factors) are examined in connection with the so-called atomicity assumption of crystallography. Using molecular orbitals previously computed by direct numerical integration of momentum space Hartree-Fock equations for the H-2 and Li-2 molecules, the patterns of parallel and perpendicular form factors with respect to bond axes are shown to be more significant than are the corresponding spherical averages. The case of the triatomic system H-3 is briefly considered. (C) 1997 John Wiley & Sons, Inc.