THE ELECTRONIC-STRUCTURE OF CRYSTALLINE LITHIUM HYDRIDE - A REDUCED DENSITY-MATRIX APPROACH

Three directional Compton profiles J(q) of LiH were measured by means of Am-241 gamma-ray scattering. The Fourier transforms (reciprocal form factors B(s)) were compared to the results from Lowdin-orthogonalised wavefunctions and from a full solid-state RHF calculation performed with the program CRYSTAL for various basis sets of different quality. The wavefunction that yielded best agreement with the experiment was then used to calculate two-dimensional cuts through the one-electron density matrix (ODM) in the main bonding directions both for the crystal and for clusters of variable size. From the off-diagonal parts of the ODM it is possible to estimate the influence of small covalent contributions to the chemical bonding in LiH. The influence of different cluster orbitals is discussed as well as the question which cluster size already shows the main qualitative features of chemical bonding in the ODM of the crystal.