The structure of intercalated water in superconducting   Na$_{0.35}$CoO$_{2}\cdot$1.37D$_{2}$O: Implications for the superconducting   phase diagram
  We have used electron and neutron powder diffraction to elucidate the structural properties of superconducting \NaD. Our measurements show that our superconducting sample exhbits a number of supercells ranging from ${1/3}a^{*}$ to ${1/15}a^{*}$, but the most predominant one, observed also in the neutron data, is a double hexagonal cell with dimensions \dhx. Rietveld analysis reveals that \deut\space is inserted between CoO$_{2}$ sheets as to form a layered network of NaO$_{6}$ triangular prisms. Our model removes the need to invoke a 5K superconducting point compound and suggests that a solid solution of Na is possible within a constant amount of water $y$. 
D. N. Argyriou (1), C. J. Milne (1), N. Aliouane (1), P. G. Radaelli   (2), L. C. Chapon (2), A. Chemseddine (1), J. Veira (...