| Summary: | A new sodium manganese-nickel phosphate of alluaudite supergroup with the general formula NaMnNi<sub>2</sub>(H<sub>2/3</sub>PO<sub>4</sub>)<sub>3</sub> was synthesized by a hydrothermal method. The synthesis was carried out in the temperature range from 540 to 660 K and at the general pressure of 80 atm from the oxides mixture in the molar ratio MnCl<sub>2</sub>: 2NiCl<sub>2</sub>: 2Na<sub>3</sub>PO<sub>4</sub>: H<sub>3</sub>BO<sub>3</sub>: 10H<sub>2</sub>O. The crystal structure was studied by a single-crystal X-ray diffraction analysis: space group <i>C</i>2/<i>c</i> (No. 15), <i>a</i> = 16.8913(4), <i>b</i> = 5.6406(1), <i>c</i> = 8.3591(3) Å, <i>β</i> = 93.919(3), <i>V</i> = 794.57(4) Å<sup>3</sup>. The compound belongs to the alluaudite structure type based upon a mixed hetero-polyhedral framework formed by <i>MX</i><sub>6</sub>-octahedra and <i>TX</i><sub>4</sub>-tetrahedra. The characteristic feature of the title compound is the absence of cations or H<sub>2</sub>O molecules in channel II, while the negative charge of the framework is balanced by the partial protonation of PO<sub>4</sub> tetrahedra. The presence of the transition metals at the <i>A</i>-type sites results in the changes of stoichiometry and the local topological features. Topological analysis of the hetero-polyhedral alluaudite-type frameworks and its derivatives (johillerite-, KCd<sub>4</sub>(VO<sub>4</sub>)<sub>3</sub>-, and keyite-type) and quantitative characterization of their differences was performed by means of natural tilings.
|
|---|
