Electronic properties of the eletride-type molecule Li(9-crown-3)2. Comparison of Hartree-Fock and local density approximations: implications for crystalline crown ether electrides

We consider the title molecule and its positive ion and calculate the HOMO charge density for the neutral molecule and the potentials for the positive ion, using the Hartree-Fock (HF) and local density approximation (LDA). Both approximations suggest that the ground state of the neutral is Rydberg-like with a spatially extended HOMO charge density with the LDA density considerably more compact than the HF. We analyze this difference in terms of the potential energy seen by the HOMO electrons in the two approximations.