X-ray high temperature powder diffraction study and computer simulation ofgamma-LiNaCO3

The high-temperature gamma-phase of lithium sodium carbonate (gamma-LiNaCO3 , a = 8.311 Angstrom, c = 3.386 Angstrom, P (6) over bar) has been studied by X-ray diffraction and computer simulation methods. The results of comput er simulation based on the ionic model and the temperature dependence of th e superlattice reflection intensities correspond to the order-disorder type of the beta-gamma phase transition. The Rietveld refinement using X-ray po wder data at 713 K confirms the disordered model of the structure with one of the three CO32- groups disordered over two sets of positions.