Premium
The ab initio structure determination of Sigma‐2 (a new clathrasil phase) from synchrotron powder diffraction data
Author(s) -
McCusker L.
Publication year - 1988
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889888002092
Subject(s) - synchrotron , powder diffraction , diffraction , crystallography , ab initio , phase (matter) , x ray crystallography , atom (system on chip) , chemistry , oxygen atom , sigma , materials science , physics , molecule , optics , computer science , organic chemistry , quantum mechanics , embedded system
The structure of Sigma‐2 ([Si 64 O 1 28 ].4C 10 H 17 N), a new clathrasil phase, has been determined directly from synchrotron X‐ray powder diffraction data using no prior structural information. The high‐resolution data were collected at the NSLS in Brookhaven, and then processed through a series of computer programs assembled and modified for this purpose. There are four Si and seven O atoms in the asymmetric unit, and nine of the 11 framework‐atom positions appeared in the direct‐methods solution. Eight of these were used to generate a Fourier map which clearly showed the remaining three oxygen positions. A whole‐pattern refinement in the space group I 4 1 / amd [ a = 10.2387(1) and c = 34.3829(1) Å] converged with R F = 0.100, R wp = 0.225 and R exp = 0.190. The designation SGT for this new zeolite structure type has been approved by the IZA Structure Commission. Neither of the two cages which make up Sigma‐2 has been encountered previously. The 1‐aminoadamantane used in the synthesis was found to be disordered in the large cage. The JCPDS Diffraction File No. is PDF39‐2000.