High-resolution nuclear magnetic resonance (NMR) spectra and synchrotron x-ray powder diffraction data have been obtained from a well-crystallized highly dealuminated sample of the zeolite ZSM-11. The Rietveld profile technique has been applied to the synchrotron data to give the first detailed refinement of the idealized structure derived ten years ago by distance least-squares modeling methods [G. T. Kokotailo, P. Chu, S. L. Lawton, and W. M. Meier, Nature 275, 119 (1978)], which involves 54 variable atomic positional parameters. The structure is tetragonal (a = 20.065 Å, c = 13.408 Å at 25 °C) and consistent with the previously reported tetragonal space group I \overline 4 m2, but the NMR spectra indicate local deviations from this symmetry that disappear at 100 °C.
