Influence of water intercalation on the electronic structure of the   hydrated Na0.3CoO2.yH2O using a local spin density approximation
  The electronic band structures of the parent compound Na0.3CoO2 and the hydrated superconductor Na0.3CoO2.1.3H2O were evaluated using the local spin density approximation (LSDA). Systematic analysis on the bands near the Fermi surface (FS) revealed that the hydration-induced modifications appear, notably in the valence charge density and the orbital hybridization. The most striking changes are the decrease of density in Cobalt's a1g state and the rehybridization between O 2p and Co a1g in the hydrated superconducting phase. These hydration-induced modifications could yield visible differences in interband excitations and dielectric functions. Experimental results of electron energy-loss spectroscopy (EELS) are fundamentally in agreement with the theoretical predictions for the hydrated Na0.3CoO2.yH2O. 
R. J. Xiao, H. X. Yang and J. Q. Li