Aragonite-type lanthanum orthoborate, LaBO3

The crystal structure of the low-temperature ( LT) modification of LaBO3 has been redetermined from single-crystal X-ray data; the resulting structure confirms the previous study [Abdullaev, Dzhafarov & Mamedov (1976). Azerbaidzhanskii Khim. Zh. pp. 117 - 120], but with improved precision. LT-LaBO3 crystallizes in space group Pnma and adopts the aragonite-type structure. Except for one O atom, which is situated on a general position, all other atoms ( one La, one B and a second O atom) lie on mirror planes. The structure is composed of LaO9 polyhedra with an average La - O distance of 2.593 angstrom and trigonal BO3 groups with an average B - O distance of 1.373 angstrom. Slight anisotropies of the thermal vibrations of La and B atoms suggest that the electrostatic La (. . .) La and La (. . .) B interactions across the shared edges are weak.