FIRST-PRINCIPLES STUDY OF THE ELECTRONIC-STRUCTURE OF NAXHYC60

We investigated theoretically the electronic structure of a new C-60 b ased superconductor, NaxHyC60 where x similar to 3.6 and y similar to 1, to provide criteria that enable one to identify which of two possib le phases, Na3HC60 and Na4HC60, is important to the superconductivity. Studying these two phases by using the first-principles calculations, we found remarkable differences in the electronic structures between them, especially in the partial densities of states and the nuclear-qu adrupole interaction of Na-23. We propose that these quantities can wo rk as the criteria for the identification.