A NOVEL POTASSIUM-RICH VARIETY OF TINSLEYITE K1.5(H2O)0.5[Al2(OH){(OH)0.5(H2O)0.5}(PO4)2]статья
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Дата последнего поиска статьи во внешних источниках: 19 июля 2013 г.
Аннотация:Crystals of a potassium-rich variety of the mineral tinsleyite were obtained by hydrothermal synthesis in the system K2O–Al2O3–P2O5–H2O. The new phase is monoclinic, sp. gr. P21/n, a = 9.4352(7), b = 9.5254(10), c = 9.4309(7) Å, = 101.421(7)O, Z = 4. Its crystal structure was solved from single-crystal data collected at 193 K and refined to R = 0.0293, including positions of all hydrogen atoms. The crystal structure is built from units of four AlO6 octahedra sharing edges and vertices. The octahedral units are crosslinked by PO4 tetrahedra to form a three-dimensional framework with channels along the main crystallographic [010], [001] and [100] directions, where the large K+ ions and H2O molecules are distributed. The system of O – H . . . O asymmetric hydrogen bonds between H2O molecules, hydroxyl groups and framework oxygen atoms provides additional crosslinking in the structure. It has been shown that a change in the alkalinity of the mineral forming system correlates with the composition of the crystallizing phase and simultaneously influences the character of hydrogen bonding. The new K-rich variety of the tinsleyite is suggested as a possible mineral species. The crystal chemistry of the leucophosphite mineral group and the related synthetic compounds is discussed.