Compton profile anisotropies in diatomic molecules and solids

A theoretical calculation of Compton profiles and Compton profile anisotropies in a diatomic molecule using LCAO-MO-SCF (near-Hartree Fock) wavefunctions is presented. The different occupied molecular orbitals (MO) give interesting profiles and anisotropies which are indicative of their roles in the binding of the molecule. The results for the diatomic molecule are extended to approximate a face-centered-cubic (FCC) diatomic crystal using a molecular simulated crystal (MSC) procedure in which the outermost MO's are modified to match the symmetry of the crystalline environment. The resulting Compton profiles are called Symmetry Resolved Profiles (SRP). This formalism is applied in detail to lithium fluoride (LiF) at an internuclear separation of 3.55 a.u., approximately the crystalline spacing. The results compare favorably with previous anisotropy calculations and experiment. The next crystal studied is lithium hydride (LiH). There is fair agreement between theory and experiment. There are no other reported theoretical calculations for LiH. Results for a number of alkali halides are then presented and trends in the anisotropies in relation to the ionic or covalent character of the molecules are indicated. Spherically-averaged total Compton profiles are also compared with experiments on polycrystalline (isotropic) samples. Good agreement is found in each case considered.