Comparison of the electronic structures of hydrated and unhydrated NaxCoO2:The effect of H2O

Abstract

We report electronic structure calculations within density functional theory for the hydrated superconductor ${\mathrm{Na}}_{1∕3}{\mathrm{CoO}}_{2}1.33{\mathrm{H}}_{2}\mathrm{O}$ and compare the results with the parent compound ${\mathrm{Na}}_{0.3}{\mathrm{CoO}}_{2}$. We find that the intercalation of water into the parent compound has little effect on the Fermi surface outside of the predictable effects of expansion, in particular increased two dimensionality. This implies an intimate connection between the electronic properties of the hydrated and unhydrated phases.