... pseudosymmetry, the structure is monoclinic (space group C 2) with a = 26.0388(10), b = 15.0651(8), c = 15.5361(8) Å, β = 90.48(1)°, and V = 6094.2(5) Å 3 . The refinement of an anisotropic model led to an R index of 0.0656 for 7143 observed reflections [ I > 2σ( I )] and 0.0759 for all 17 447 independent...

...Paola Bonazzi; Giulio I. Lampronti; Luca Bindi; Stefano Zanardi Abstract The crystal structure of the rare mineral wakabayashilite was solved by direct methods using intensity data collected from a twinned crystal. This study revealed that, in spite of the strong hexagonal pseudosymmetry...

..., B 2 O 4 (OH). Each octahedral chain has a strong twofold screw pseudosymmetry parallel to the c axis. The pseudosymmetry is such that the chain is nearly perfectly transformed by the screw operations into itself with average atomic displacement of only 0.056(4)Å. This situation theoretically permits...

... is good parallel to {100}. The atomic structure is an extreme example of dense-packing where both O 2- and Ca 2+ ions comprise the dense-packed layers. The [MgO 6 ] octahedra are linked at every corner by [SiO 4 ] tetrahedra, defining a “pinwheel” of 3 m point pseudosymmetry. The pin wheels link...

... to the pronounced pseudosymmetry, indicates preference for an ordered pattern where Al and Si are distributed on alternating tetrahedra [ d Si–O/ d Al–O = 1.628(1)/1.719(1) Å], so that every SiO 4 tetrahedron is coordinated to four AlO 4 tetrahedra and vice versa . The alternating distribution was independently...

...Paola Bonazzi; Fiorenzo Mazzi Abstract The crystal structure of bottinoite, Ni(H 2 O) 6 [Sb(OH) 6 ] 2 , was determined from a twinned crystal. This study revealed that the strong 3 1 m pseudosymmetry shown by all the natural and synthetic crystals examined results from {10 1 0} twinning...

...P. Bonazzi; D. Borrini; F. Mazzi; F. Olmi Abstract The crystal structure of synthetic pääkkönenite, Sb 2.07 As 0.93 S 2.00 , was determined. This study revealed that, in spite of the strong orthorhombic pseudosymmetry shown by Weissenberg photographs, the structure is monoclinic (space group C 2/ m...

... on the side withprojecting rings. A pseudosymmetry is dominant in the structure; the two halves of the polyanion as well as two Na atoms are quasi-equivalent. Two of the Na atoms and the hydrogen bonding arrangement do not follow the pseudosymmetry. 1 Paper presented at the XXVII Congress...

... crystal systems but showing a pseudosymmetry should show the prefix ‘pseudo-’. (iii) Polymorphs with the same crystal system but different space groups are distinguished by the prefix ‘para-’. If three or more polymorphs show the same crystal system but different space groups, the space group notation may...

... , a ≈ 14.1, b ≈ 14.2, c ≈ 9.9 Å) and PHI ( P 2 1 / m , a ≈ 9.9, b ≈ 14.3, c ≈ 8.7 Å, β = 124.8°) frameworks of similar composition are assembled from identical tetrahedral units, though with a different connectivity. Coherent intergrowth and twinning of the two frameworks lead to P 4 2 / mnm pseudosymmetry...

... is a desymmetrized OD structure with profuse twinning. The two types of layers present possess layer symmetries p 1̅ and b 2/ m 11, respectively. These layers respectively have a pseudoperiodicity equal to a /2 and a set of elements of pseudosymmetry which together cause a disorder process. Abstract Nous avons...

... pseudosymmetry mm 2, which is usually adopted for M2 in silicate olivines. The energy difference, δ̄ e , between I. and II. represents the low-symmetry splitting of the excited state 5 E g of octahedral Fe 2+ under m3m. Polarization-averaged energies of the above transition I. and of δ̄ e increase with iron...

... of stereochemical and bond-valence arguments. The structure displays strong Pbca pseudosymmetry, especially among the U atoms. The lower symmetry is primarily due to H-bond interactions between interlayer H 2 O groups and O(uranyl) atoms of the structural sheet. © 1996 Mineralogical Association of Canada 1996...

..., and on prehnite and epidote coexisting with pumpellyite. Spectroscopic data for prehnite, presented for the first time, are discussed in light of the pseudosymmetry of its structure. The data clearly show the prevailing role of Fe (super 3+) in the crystal chemistry of the paragenetically associated Ca-silicates...

... determined. They are interpreted in terms of crystal field theory using the strong field scheme. Spin-orbit coupling and fourth-order terms were included in the calculation. For Fe 2+ at M2, a pseudosymmetry of mm 2 was assumed. Using the covalency factor α 2 , z e 2 〈 r 2 〉, and z e 2 〈 r 4 〉 as adjustable...

... is similar to that found in close-packed structures. A marked pseudosymmetry (towards the centric group Pcan ) is present in the Sb–O sheet. Copyright © 1980 by the Mineralogical Society of America 1980 ...

... are: a = 8.012(2), b = 15.956(4), c = 6.801(2) A , β = 96.60(3)°; Z = 8. A strong P 2 1 / n pseudosymmetry appears in the structure, yet the average pseudo-center is slightly shifted from the correct position 1/4, 0, 1/4 in space group P 2 1 / n . The structure is built up by (010) layers of AsO 4 and MnO 6...

...). The structure consists of tetrahedral layers parallel to (001), superposed at intervals of c /2 and connected by cation polyhedra (RE,Na,Ca-antiprisms and Fe,Mn-octahedra). The {110} twinning, always present and responsible for the tetragonal pseudosymmetry, is explained on structural grounds. The structure...