| Summary: | Simulation of diffraction patterns for 1D disordered crystals was used to investigate the structure of the initial CO<sub>3</sub><sup>2−</sup> containing MgGa LDHs with a different Mg<sup>2+</sup>/(Mg<sup>2+</sup> + Ga<sup>3+</sup>) ratio equal to 0.67, 0.75, and 0.80; mixed oxides obtained by calcination of LDHs at a temperature of 550 °C; and the hydroxide obtained by hydration of MgGa oxide with the Mg<sup>2+</sup> content of 0.80. The initial LDHs contain lamellar inclusions of manasseite structure (polytype 2H<sub>1</sub>) in the hydrotalcite structure (3R<sub>1</sub>). A loss of water at 200 °C leads to the formation of a metastable dehydrated phase where layers are packed, as in polytypes 3R<sub>2</sub> and 1H, with turbostratic disorder. The structure of mixed oxides is also layered and consists of periclase-like octahedral layers and spinel-like octahedral-tetrahedral layers. Hydration of the oxides results in restoring the initial layered hydrotalcite structure (polytype 3R<sub>1</sub>) for Mg<sup>2+</sup> mole fractions 0.67 and 0.75. For the Mg<sup>2+</sup> content of 0.80, the phase composition is represented by the hydroxide with hydrotalcite structure and the layered mixed hydroxide with the alternation of hydrotalcite and brucite lamellar domains, which was also revealed by calculation of diffraction patterns using models of 1D disordered crystals.
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