Band 163, Heft 3-4

C 26 H 27 NO 5 is monoclinic, space group P 2 1 / n with a = 10.313(2), b = 23.816(7), c = 9.847(2) Å, β = 103.94(3)°, V = 2347.3 Å 3 , Z = 4, D c = 1.227, D 0 = 1.23 Mg m −3 , F (000) = 920, μ = 0.654mm −1 , λ (Cu Kα ) = 1.5418 Å. The final R is 0.047 for 3582 observed reflexions. The configuration around the chiral centers C(2), C(3), C(10), C(9) of the dihydroxyfuryl rings is R,R,S,S. The molecules are held together by a hydrogen bond O – H … O and normal van der Waals contacts.

Sphere configurations and partitions of three-dimensional space into Dirichlet domains have been studied for the point configurations of the trigonal lattice complex R [unk] m 6(c). In total, 11 sphere-configuration types and 12 types of Dirichlet partitions have been derived. Utilizing the concepts of Hoppe (1970, 1979) and O'Keeffe (1979), coordination numbers for this two-dimensional field have been calculated.

In rose-colored natural quartz crystals two new hole centers were detected and analyzed by electron paramagnetic resonance (EPR). A hole center with characteristic doublet and sextet hyperfine structures was identified as an O − ion bridging between a substitutional aluminum and phosphorus atom each. This center slowly bleaches in UV light and can be enhanced by X-ray irradiation. It is most likely responsible for the rose coloration and also explains the repeatedly reported bleaching of “rose” quartz in daylight. Light-induced transfer of the hole in the PO 4 , not the AlO 4 unit is assumed to cause this strong visible absorption. Several features of this center are quite unexpected: The localization of the hole between Al and P contradicts electrostatic considerations. It is evidently caused by the longer Al … O distance resulting from substitution of Si by the smaller P. This longer distance also explains why this center is still observable by EPR at room temperature in contrast to the unperturbed Al … O − (smoky quartz) center. It also has an unexpectedly high thermal stability compared to aluminum-related hole centers with nearby positive ions. All the phosphorus present is obviously associated with aluminum, in agreement with estimates of the equilibrium distribution based on a purely Coulomb attraction between Al 3+ and P 5+ on sites of Si 4 + . The isotropic 27 Al superhyperfine structure is four times smaller than in the unperturbed smoky quartz center, evidently as a result of the strong electron attraction by the pentavalent phosphorus opposite to Al which also gives rise to a large and practically isotropic 31 P doublet superhyperfine splitting.

Structural description in terms of frameworks – three-dimensional periodic arrangements of points which are occupied by atoms – is used as the basis of analysing the cell dimensions of phases with the MgCu 2 structure (cubic) in terms of the elemental diameters of the component atoms. The MgCu 2 structure is described in terms of interpenetrating homogeneous D and T′ frameworks or the heterogeneous [D + T′] framework. The relative influences of the atoms occupying these three frameworks on the cell dimensions of different groups of phases that show distinct dimensional behaviour are determined. The self-coordination of atoms on the T′ framework is six. Some interesting observations are made on whether the basic diameters of atoms on this framework might correspond to a coordination number of six rather than twelve which is the overall coordination number of the atoms on the framework (T′).

An equation is proposed to calculate the observed cell constants of β -W-(MN 3 ) structures in terms of framework W occupied by the N atom with diameter D N for CN12. A contraction term K N has to be added. The influence of the M atoms is of diameter D M minus the size of occupied icosahedral void d M , multiplied with the inclination factor f M for each type of N atoms. The f M factors are taken from the plot a obs against D M .

Ikaite, CaCO 3 · 6H 2 O, is monoclinic, C 2/ c , with a = 8.792(2), b = 8.310(2), c = 11.021(2) Å, β = 110.53(5)°, Z = 4. With 2205 independent reflections taken at −25°C of a naturally grown crystal specimen the structure was refined to a weighted R w = 0.028. The CO 3 group is planar with C – O distances 1.279(2) and 1.290(1) (2 ×) Å. The hydrogen bond network is determined. The optical behaviour is explained by structural characteristics.

A method for measuring piezoelectric constants by a dynamic method operating at frequencies of about 3 – 5kHz is described. It is characterized by simple handling and evaluation of the piezoelectric constants d ijk and their sign, high accuracy (<1%) and the possibility of piezoelectric measurements on semiinsulating ( ϱ ≥ 10 9 Ω cm) crystals. The method is based on the inverse piezoelectric effect. The piezoelectrically induced deformation of the test crystal is detected by a piezoelectric ceramic and compared with that of a standard crystal ( α -quartz). Piezoelectric coefficients of some substances are redetermined. Values for the d ijk of CdTe and N 2 H 5 LiSO 4 are given.

A group theoretical procedure to determine the non-characteristic orbits is described. For the 230 three-dimensional space group types all non-characteristic orbits were determined. Two examples for the space groups Pbam and P 3 1 12 are given.

Single crystals of the isotypic compounds KMgP 3 O 9 , KZnP 3 O 9 , and KCaP 3 O 9 (benitoite-type) with dimensions up to 35 mm have been grown from the melt. Because of the high viscosity of the melts a special growth method was necessary. The linear electrooptical tensor [ r ijk ] and the tensor of the linear electrostriction [ d ijk ] have been determined: r 222 = 0.17(2), d 222 = 0.51(2) (KMgP 3 O 9 ); r 222 = 0.13(3), d 222 = 0.32(3) (KZnP 3 O 9 ; r 222 = −0.23(3), d 222 = 1.83(5) (KCaP 3 O 9 ) (unit: 10 −12 m/ V , T = 295 K, γ = 633 nm).

Large single crystals of optical quality of Ca[Sb 2 {(+)-C 4 H 2 O 6 } 2 ] · 2H 2 O and Sr[Sb 2 {(+)-C 4 H 2 O 6 } 2 ] · 2H 2 O (point group 6) have been grown from aqueous solutions by isothermal evaporation at 95°C (65°C). The linear electrooptical tensor [ r ijk ] and the tensor of the linear electrostriction [ d ijk ] have been determined for both crystals: d 311 = +1.72(7), d 333 = −1.12(8), d 113 = +0.76(5), d 213 = −4.39(5), r 113 = +1.28(3), r 333 = −0.25(4), r 131 = −0.23(2), r 132 = −0.18(4) (Ca-compound); d 311 = −1.55(7), d 333 = −1.70(7), d 113 = −1.58(4), d 213 = −1.76(4), r 113 = −2.03(2), r 333 = −0.54(2), r 131 = −0.05(2), r 132 = +0.29(3) (Sr-compound) (unit: 10 −12 m/ V , T = 295K, λ = 633 nm).

The crystal structure of Sr[Sb 2 {(+)-C 4 H 2 O 6 } 2 ] · 2H 2 O has been determined at room temperature by X-ray diffraction. The compound crystallizes in space group P 6 4 with a = 9.136(2). Å, c = 15.680(5) Å, V = 1133.4 Å 3 , D m = 2.89 Mg m −3 , D c = 2.898 Mg m −3 , Z = 3. The structure has been solved by Patterson and Fourier methods and refined by least-squares calculations to a final R value of 0.025 for 1861 reflexions [(| F 0 | ≥ 4σ ( F 0 )]. The main structural feature is the tartrato(4–)-bridged binuclear complex [Sb 2 {(+)-C 4 H 2 O 6 } 2 ] 2− . The compound is isostructural with the analogous calcium salt.

The crystal structure of the monoclinic form of ilvaite has been investigated. A crystal from Tsumo, Japan, was characterized by space group P 2 1 / a , with a = 13.009(1) Å, b = 8.8008(3) Å, c = 5.8589(2) Å, β = 90.324(9)°, whereas a crystal from Techukhe, Siberia, had P 2 1 / a , a = 13.013(3) Å, b = 8.8197(6) Å, c = 5.8424(5) Å, β = 90.03(1)°. In the structure, the octahedra formed by oxygen atoms about Fe(11) and those about Fe(12) are alternately linked together, sharing edges to form a chain of octahedra parallel to c . The monoclinic symmetry of ilvaite is characterized by ordering of Fe 2+ and Fe 3+ which are distributed over these two Fe sites with a ratio of 1:1. The atomic contents in the Fe(11) site, estimated from mean Fe(11) – O length, are: Tsumo ilvaite 0.85 Fe 2+ and 0.15 Fe 3+ , and Techukhe ilvaite 0.53 Fe 2+ and 0.47 Fe 3+ . From these atomic occupancies, the order parameter, σ , of Tsumo ilvaite is calculated to be 75%, while that of Techukhe ilvaite 6%. From the two cases of monoclinic ilvaites, a relation between β and σ has been deduced; the result permits predicting β ≈ 90.45° for an ilvaite crystal having σ = 100%. The orthorhombic form of ilvaite may be defined as a form of ilvaite having σ = 0.

The molecular and crystal structure of perdeuteronaphthalene was refined from neutron diffraction data collected at 12 K on an automatic four-circle diffractometer. The monoclinic space group P 2 1 / a remains unchanged, lattice constants at 12 K are: a = 8.096(7), b = 5.941(5), c = 8.648(7) Å, β = 124.63(5)°, Z = 2, μ ( λ = 1.26 Å) = 0.095 cm −1 . 907 symmetry-independent reflections up to sin θ / λ = 0.72 Å −1 refined to R w ( F ) = 0.044. The C 10 D 8 molecule is planar with a maximum distance of atoms from a least-squares plane of 0.008 Å. Mean distances are C – C = 1.371 – 1.432 Å, C – D = 1.091 – 1.095 Å. The refined structure is compared to a structure calculated from atom pair potentials.

The crystal structure of Sr 2 MgSi 2 O 7 with tetragonal, a = 7.9957(10), c = 5.1521(9) Å, Z = 2, space group P [unk]2 1 m has been refined to R = 4.3% from three-dimensional single-crystal, X-ray diffraction data by full-matrix least-squares calculations. This compound is completely isomorphous with åkermanite, Ca 2 MgSi 2 O 7 , and the Mg and Si atoms are distributed respectively in the T(1) and T(2) sites of the melilite structure. The tetrahedral Mg – O bond length (1.942 Å) is clearly longer than that in Ca 2 MgSi 2 O 7 (1.915 Å), which exhibits the flexibility of T(1) site in melilite structures. In the system Ca 2 MgSi 2 O 7 – Sr 2 MgSi 2 O 7 the tetragonal parameters of the solid solutions are linear functions of molar compositions, which implies that this solid solution is continuous. All of the rare silicates with tetrahedrally coordinated Mg cations contain alkali or alkali-earth cations in their structures and the ratios Mg: Si are below one.

Preliminary X-ray data on NH 2 CH 2 COOH · Ca(NO 3 ) 2 · 2H 2 O show that the crystal belongs to the orthorhombic system with four molecules per unit cell. The unit cell dimensions are a = 6.865(5), b = 13.250(10), c = 11.275(6) Å. The space group is P 2 1 2 1 2 1 . The IR spectra show that the glycine molecules exist in the zwitterionic form inside the lattice.