The crystal structure of brazilianite, NaAl3(PO4)2(OH)4

The mineral brazilianite, NaAI3(PO4)2(OH)4, is monoclinic, space group P21/n, with a = 11.233 (6), b = 10"142 (5), c=7-097 (4) ,& and fl=97.37 (2) A~. With Z = 4 the calculated density, 2.998 (4), compares well with the measured density, 2.98 (1) gcm -3. The structure was solved by direct phasing and Fourier techniques. Of the 2276 unique reftexions collected by counter methods, 2033 with I> 3a(l) were used in the least-squares refinement to R=0-030 (wR=0-050). Brazilianite is composed of chains of edgesharing AI-O octahedra linked by P-O tetrahedra, with Na located in cavities in the framework.