On the chemical interpretation of the one-electron density matrix of some ionic solids: LiH, LiF, and LiFHF

Two-dimensional cuts through one-electron density matrices of three ionic solids in the position representation were calculated from restricted Hartree-Fock wavefunctions. The basis-set quality was assessed by comparison of calculated Compton profiles/reciprocal form factors with experimental ones. The off-diagonal regions of the density matrix contain the main information about chemical bonding in the crystal. The decomposition of the total density matrix into band contributions shows that the valence band always dominates in those regions. Furthermore, one-electron density matrices of small subunits of the crystal and of symmetrically orthogonalised crystal wavefunctions were calculated. Their similarity and differences with respect to the solid are discussed.