does anyone knows the atomic positions for PDF No. 33-1229 alpha-Na2Ca4(PO4)2SiO4 Space-group P-3m1 or where I can find it? I coudn't find in the ICSD database 2/2004.
Producing a calculated powder pattern from 33-1229 and using a search/match software suggests that this compound is highly related to the mineral Nagelschmidtite (03-9796), itself of "unknown" structure, and to Ca2SiO4 (86-0401), well known... The fit on the figure is obtained after some cell parameters tuning : http://sdpd.univ-lemans.fr/33-1229.jpg
The ICDD-JCPDS PDF is a mine for solving structures said to be unknown in the PDF ;-). A pity that the guys at the ICDD-JCPDS do not check their own data against their own data ;;;-).
Best wishes,
Armel
