Temperature dependence of the ²³Na-central lineshape in Na₂CO₃ studied by nuclear magnetic resonance

The temperature dependence of the ²³Na central lineshape of Na₂CO₃ has been observed by NMR. At the phase transitions at T_cl=763K and T_c2=633K there is no change of the distorted octahedral oxygen environment of the sodium ions observable. But changes of this oxygen environment far below T_c2 and above T_c1 were observed to occur in contrast with structural investigated. The temperature dependence of the quadrupole frequency nu _Q in beta -Na₂CO₃ is explained by stretch vibrations of the CO²/₃^- groups along the C-O bond.