Peter Held

Crystal Growth and Optical Properties of the Polar Hydrated Pentaborates Rb[B5O6(OH)4] . 2H2O and NH4[B5O6(OH)4] . 2H2O and Structure Redetermination of the Ammonium Compound

Large single crystals of the polar, hydrated pentaborates Me[B 5 O 6 (OH) 4 ].2H 2 O (Me = Rb, NH 4 ) were grown from aqueous solutions. The structure of NH 4 [B 5 O 6 (OH) 4 ].2H 2 O was redetermined and proved to be orthorhombic (space group Aba2 (No. 41) with a = 11.3192(7) A, b = 11.0261(8) A, c = 9.2316(5) A, V = 1152.2(1) A 3 , D x = 1.569 Mgm -3 , Z = 4, M = 272.15 gmol -1 , R(F) = 0.0369 for 1266 unique reflections (I ≥ 4σ (I)), isomorphous with the potassium and rubidium compounds. Refractive indices between 365 nm and 1100 nm as well as unpolarized absorption spectra of NH 4 [B 5 O 6 (OH) 4 ].2H 2 O and Rb[B 5 O 6 (OH) 4 ].2H 2 O were determined and phase-matching curves for second-harmonic generation were calculated. Both compounds allow type I and type II phase-matching at wavelengths from about 450 nm to the near infrared region.

Improved Single Crystal Growth of the Boron Sillenite “Bi24B2O39” and Investigation of the Crystal Structure

The boron sillenite, up to now known as the 12:1 compound Bi 24 B 2 O 39 in the system Bi 2 O 3 - B 2 O 3 and crystallizing in the space group 123, melts incongruently at 655 °C only about 25 K above the eutectic tie line and corresponding to a steep liquidus line. Single crystals with dimensions larger then 1 cm 3 have been successfully grown in [100], [110], and [111] direction by an improved Top Seeded Solution Growth (TSSG) technique equipped with crucible weighing, accelerated crystal rotation technique and air-cooled pulling rod. The structure of the boron sillenite was analyzed by X-ray diffraction method, which was possible due to the high crystalline quality achieved. A defect-free sublattice corresponding to a Bi-O framework is isostructural with all sillenites, but a 2 A environment around the origin is occupied by different cations with different population coefficients. The best calculation results in the formula Bi 24.5 BO 38.25 which is more Bi-rich than the 12:1 assumption.

New compounds of glycine with metal halogenides

Abstract The crystal structures of five new glycine (H2N–CH2–COOH) metal halogenide compounds were determined by single crystal X-ray diffraction. Three of them are monoclinic phases, GlycineCaCl2 · 3 H2O (space group P21/c, a = 9.964(2), b = 6.868(1), c = 13.959(3) Å, β = 104.11(3)°, R1 = 0.024), GlycineZnCl2 · H2O (space group P21/a, a = 7.868(1), b = 9.124(1), c = 10.645(1) Å, β = 103.51(1)°, R1 = 0.026) and Glycine2ZnCl2 · 2 H2O (space group C2/c, a = 14.444(1), b = 6.916(1), c = 12.968(1) Å, β = 117.90(3)° R1 = 0.033), two of them are orthorhombic phases Glycine3CeCl3 · 3 H2O (space group P212121, a = 4.788(1), b = 12.074(2), c = 30.949(6) Å R1 = 0.034) and Glycine2CaI2 · 3 H2O (space group Pca21, a = 13.059(3), b = 9.862(2), c = 22.724(5) Å R1 = 0.023). The atomic arrangements as well as aspects of the crystal chemistry of these compounds are presented.

Cerium triborate, CeB3O6

CeB3O6 crystallizes in the monoclinic space group I2/a and is a member of the isostructural series REB3O6 (RE = La, Pr, Nd, Sm, Eu, Gd, Tb). The structure consists of chains of [B6O12]n6− building units, that run parallel to the c axis, and tenfold coordinated Ce3+.

Polar potassium rare earth nitrates K2[RE(NO3)5(H2O)2] (RE = La, Ce, Pr and Nd). I. Crystal growth and crystal structures

Using a standard evaporation technique at 311 K, large single crystals of the polar orthorhombic potassium rare earth nitrates K2RE(NO3)5.2H2O, where RE = La, Ce, Pr or Nd, of optical quality and dimensions up to 5 × 5 × 4 cm, were grown from aqueous solutions containing a stoichiometric ratio of potassium and rare earth ions (K:RE = 2:1) and a surplus of nitric acid. Detailed structural and crystal chemical analyses of all four isomorphic compounds based on single-crystal X-ray diffraction data were carried out [space group Fdd2; Z = 8; La compound: a = 11.2814 (6), b = 21.480 (1), c = 12.2589 (4) A, R = 0.94%; Ce compound: a = 11.263 (3), b = 21.404 (3), c = 12.230 (4) A, R = 1.92%; Pr compound: a = 11.213 (2), b = 21.392 (4), c = 12.204 (2) A, R = 1.58%; Nd compound: a = 11.197 (1), b = 21.378 (1), c = 12.195 (1) A, R = 1.55%]. The main structural feature is the diaquapentanitratolanthanide(III) group, [RE(NO3)5(H2O)2]2−, as stated earlier by Eriksson, Larsson, Niinisto & Valkonen [Acta Chem. Scand. Ser. A, (1980), 34, 567–572] for the La compound. The rare earth atoms are surrounded by 12 O atoms, two of which belong to water molecules, the remaining ten belonging to five bidentate nitrate groups. The coordination polyhedron [REO12] is a distorted icosahedron; its geometry is discussed using a simple hard-sphere model.

On racemic and L-malates: a comparison of their crystal structures

Abstract The crystal structures of eight different L-malates have been determined and refined from single-crystal X-ray diffraction data. The compounds are the monoclinic (space group P21, Z = 2) L-malates Ca(C4H4O5)·3H2O (a = 6.652(1) Å, b = 8.378(1) Å, c = 8.268(1) Å, β = 112.65(2)°, R = 0.027), Ni(C4H4O5)·3H2O (a = 5.762(1) Å, b = 9.006(2) Å, c = 8.406(1) Å, β = 105.54(1)°, R = 0.024), CuH2(C4H4O5)2 (a = 9.911(1) Å, b = 5.271(1) Å, c = 11.510(1) Å, β = 109.33(1)°, R = 0.031), CsH(C4H4O5)·H2O (a = 7.439(1) Å, b = 7.481(1) Å, c = 7.852(1) Å, β = 116.67(1)°, R = 0.027) as well as the four isomorphic tetragonal (space group P41212, Z = 4) L-malates MgH2(C4H4O5)2·4H2O (a = 7.524(1) Å, c = 27.459(2) Å, R = 0.041), MnH2(C4H4O5)2·4H2O (a = 7.548(1) Å, c = 27.707(2) Å, R = 0.027), CoH2(C4H4O5)2·4H2O (a = 7.519(1) Å, c = 27.537(2) Å, R = 0.030) and ZnH2(C4H4O5)2·4H2O (a = 7.533(1) Å, c = 27.360(2) Å, R = 0.029). A comparison of the atomic arrangements of L-malates with their racemic counterparts shows different aspects of symmetry as well as differences in the connectivity of the building units. In addition, for all the compounds, powder diffraction data were collected, analysed and submitted to the powder diffraction file (PDF).

Crystal growth, crystal structure and physical properties of lithium sulfamate Li[NH2SO3]

Large single crystals of the polar lithium sulfamate, Li[NH 2 SO 3 ], were grown from aqueous solution. The crystal structure was determined using single crystal X-ray diffraction data (space group: Pca2 (Nr. 29), a = 16.253(2) A, b = 5.0529(3) A, c = 8.2469(7) A, R = 0.019). Precise refractive indices were measured in the wavelength region between 0.36 μm and 1.53 μm. Above λ ≃ 0.85 μm, Li[NH 2 SO 3 ] shows optic uniaxial behaviour. A phase-matched optical second harmonic generation is not possible. Measurements of temperature dependence of thermal expansion and of main birefringences Δn (i) have given no hints for structural phase transitions in the investigated temperature region (from -130 °C to +25 °C).

Polar potassium rare earth nitrates K2[RE(NO3)5(H2O)2] (Re = La, Ce, Pr and Nd). II. Linear and nonlinear optical properties

Linear and nonlinear optical properties of the four isomorphic orthorhombic (point group mm2) potassium rare earth nitrates K2[RE(NO3)5(H2O)2], with RE = La, Ce, Pr or Nd, have been investigated. Refractive indices in a wavelength range from 0.35 to 2.5 µm and the transmission spectra between 0.25 to 3.0 µm were measured. Using the Maker fringe technique, the d_{ijk}^{\rm\, SHG} coefficients of second-harmonic generation for a fundamental of the Nd–YAP laser (λ = 1079.5 nm) were determined for all four compounds. The d_{ijk}^{\rm\, SHG} coefficients of all four substances are about three times larger than those of KDP, as was first published by Ebbers et al. [IEEE J. Quantum Electron. (1993), 29, 497–507] for K2[La(NO3)5(H2O)2]. These nitrates are promising materials for application to nonlinear optics (e.g. second-harmonic generation of Nd laser radiation). The nonlinear optical properties of these compounds seem to have their origin mainly in the nitrate groups, as indicated by a simple model (summing the molecular hyperpolarizabilities of the NO3 group). Neglecting local field effects, the hyperpolarizability of the NO3 group was calculated as β222 = 2.52 × 10−40 m4 V−1.

Monoclinic modification of polymorphic TbB3O6

Terbium triborate, TbB3O6, is confirmed to adopt at least two different structural modifications. Its monoclinic modification represents the terminal member of the isostructural series of REB3O6 with RE = La–Tb, and crystallizes in space group I2/a. The structure consists of chains of [B6O12]n6− building units, that run parallel to the c axis, and tenfold coordinated Tb3+ which link the borate chains to give a three-dimensional framework.

Linear Optical Properties of the Nonlinear Optical Complex Thiocyanates of Type Cs3MII[M2I(SCN)7] (MI = Cu, Ag; MII = Sr, Ba)

Refractive indices and their dispersion in the wavelength range from 400 to 2500 nm of the non-centrosymmetric complex thiocyanates Cs 3 Sr[Cu 2 (SCN) 7 ], Cs 3 Ba[Cu 2 (SCN) 7 ], Cs 3 Sr[Ag 2 (SCN) 7 ] and Cs 3 Ba[Ag 2 (SCN) 7 ] (space group 142m) as a basis for nonlinear optical investigation are given. All four compounds are phase-matchable in the near IR region. However, powder SHG measurements signalize only small effective coefficients for d eff SHG . In addition, information about the crystal structure and crystal growth of Cs 3 Ba[Cu 2 (SCN) 7 ] is presented.