STRUCTURE INVESTIGATION ON ANHYDROUS DISODIUM HYDROGEN PHOSPHATE USING SOLID-STATE NMR AND X-RAY TECHNIQUES

Solid-state NMR and powder X-ray diffraction techniques are combined for the resolution of structural problems in the solid state. The crystal structure of anhydrous Na2HPO4 is reexamined. Sodium-23 NMR spectra under magic angle spinning and double rotation are interpreted in terms of chemical shift and quadrupole interaction parameters. An extended Floquet theory formalism is used to calculate the spectra. The three inequivalent sodium sites found are consistent with a P2(1)/c crystal structure rather than with the previously published P2(1)/m structure. Powder X-ray data are in accordance with the NMR results and are used to obtain improved atomic coordinates.