  The structure of bundles of single-walled carbon nanotubes (SWNT) has been
refined by Rietveld analysis using neutron and X-ray powder diffraction data.
Based on previous simulation studies of powder diffraction data of SWNT and
standard Rietveld analyses, we have developed a pattern fit technique for SWNT
which provides precise structure parameters. We also show that the present
technique can be used with the maximum entropy method (MEM), which is
complementary to the Rietveld analysis. Using the neutron diffraction data of
pristine SWNT, we have successfully reconstructed the density of carbon nuclei
and zero density in the inner cavity of SWNT by MEM.
