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(CH3NH3)2CdCl4 is found to be isotructural at room temperature with (CH3NH3)2MnCl4 having the orthorhombic space group Cmca. A high temperature phase transition to a tetragonal phase could not be observed because of a decomposition slightly above 383 K. Two low temperature phase transitions are detected by means of DTA at about 283 and 173 K. The first one leads to the space group P42/ncm. A microscopic model for this phase transition is proposed. Fur die Raumtemperaturphase von (CH3NH3)2CdCl4 wird die mit (CH3NH3)2MnCl4 isostrukturelle, orthorhombische Raumgruppe Cmca gefunden. Eine Hochtemperaturumwandlung in eine tetragonale Phase konnte wegen thermischer Zersetzung oberhalb von 383 K nicht beobachtet werden. Mittels DTA werden zwei Tieftemperatur-Phasenumwandlungen bei ungefahr 283 und 173 K gefunden. Die erstere fuhrt zu einer tetragonalen Modifikation mit der Raumgruppe P42/ncm. Ein mikroskopisches Modell dieser Phasenumwandlung wird vorgeschlagen.

Optical and x‐ray observations of polyethylene have been made at high pressures and temperatures using a gasketed diamond‐anvil cell. The experiments confirm the existence of the high‐pressure phase previously postulated by Bassett and Turner. The new phase is hexagonal, with orthohexagonal lattice parameters of a = 8.46 A and b = 4.88 A. Comparison with the previously measured volume change indicates that there is a decrease in the c dimension to 2.45 A per ethylene unit in transforming from orthorhombic to hexagonal structures. The likely implication is that the molecules in the hexagonal phase do not have an all‐trans conformation. Chain‐extended growth is the result of crystallization from the melt into the hexagonal phase, whereas chain‐folded growth is the familiar process of melt crystallization.into the orthorhombic phase. Chain‐extended lamellae are observed to grow outwards behind a growing edge with a permanent narrowed profile, showing that the lamellar thickness is determined in a region extending several microns behind the growth front.

A general procedure for the calculation of the lattice modes in molecular crystals under pressure is given. Only a few modifications are necessary to the general lattice dynamical computer program. Calculations have been performed and the results are presented for naphthalene, anthracene, and orthorhombic sulphur. Although the basic program uses a sum over atom-atom interactions to derive intermolecular interactions, this is not a necessary assumption in the procedure for the application of pressure. For naphthalene and anthracene the calculated increase in phonon frequency per kilobar of pressure is roughly 0.045 and 0.12 THz for modes with frequency 2 and 6 THz, respectively. Not all modes behave in this manner, and so the calculated pressure variation could prove very useful in mode assignment. The effect of uniaxial pressure on orthorhombic sulphur was also investigated, showing a markedly different frequency variation for some modes but not for others. Thus uniaxial pressure, if experimentally possible, could prove further the success of mode assignment. At 23 kbar uniaxial pressure the orthorhombic structure of sulphur became unstable, resulting in a monoclinic form in the space group C2/c. It is of interest that the simple model for intermolecular interaction can predict a soft mode phase transition, though whether this occurs in practice remains to be seen. Ein allgemeines Verfahren fur die Berechnung der Gittermoden in Molekulkristallen unter Druck wird angegeben. Nur wenige Modifikationen sind notwendig fur das allgemeine gitterdynamische Computerprogramm. Rechnungen werden durchgefuhrt und die Ergeb-nisse fur Naphthalen, Anthrazen und rhombischen Schwefel mitgeteilt. Obgleich das Grund-programm eine Summe uber Atom-Atom-Wechselwirkungen benutzt, um die intermole-kularen Wechselwirkungen abzuleiten, ist das keine notwendige Annahme in dem Verfahren fur die Anwendung von Druck. Fur Naphthalen und Anthrazen betragt die berechnete Ver-groserung der Phononenfrequenz pro kbar Druck ungefahr 0,045 und 0,12 THz fur Moden mit einer Frequenz von 2 bzw. 6 THz. Nicht alle Moden verhalten sich in dieser Weise, und somit kann die berechnete Druckanderung sehr nutzlich sein bei der Moden-zuordnung. Der Einflus von uniaxialem Druck auf rhombischen Schwefel wurde ebenfalls untersucht, wobei sich eine merklich unterschiedliche Frequenzanderung fur einige, jedoch nicht alle Moden zeigte. Somit kann uniaxialer Druck, wenn experimentell anwendbar, den Erfolg der Modenzuordnung uberprufen. Bei 23 kbar uniaxialem Druck wird die rhombische Struktur des Schwefel instabil, und es bildet sich eine monokline Form in der Raumgruppe C2/c. Es ist interessant, das das einfache Modell der intermolekularen Wechselwirkung einen, soft'-Mode-Phasenubergang voraussagt; ob dieser aber praktisch auftritt, bleibt abzuwarten.

The phase-Q structures of Na0.98K0.02NbO3 and Na0.90K0.10NbO3 have been determined at room temperature by the neutron powder profile refinement technique. Two different models were refined: orthorhombic, space group P21ma (No. 26, in cab setting) and monoclinic, space group Pm (No. 6, in the second setting). The latter is more correct as it takes into account the splitting of the monoclinic ap and cp, but the structures can be described as very nearly orthorhombic. In the 2 mole % structure Nb atoms are all displaced by 0.18 (1) A in the same direction towards the midpoint of the edge of the surrounding octahedron. The octahedra themselves appear to be regular and are tilted by 6.8 (1)° around ap and cp and by 7.8 (1)° around bp. Na, K displacements [0.23 (4) A] are almost parallel to those of Nb. For the 10 mole % structure Na, K and Nb displacements are the same but the tilts (5.2° and 7.3°) are somewhat smaller.

The crystal structures of the title compounds, C22H30O5(I) and C22H30O4(II), have been determined by X-ray diffraction by direct methods and refined by least squares to R 0.036 and 0.043 for 1 211 and 1 204 reflections respectively. Crystals of (I) and (II) are both orthorhombic, space group P212121, Z= 4; for (I), a= 23.095(3), b= 10.987(1), c= 8.224(1)A; for (II), a= 21.199(4), b= 11.160(3), c= 8.998(2)A. The structure determinations confirm the stereochemistry previously assigned by other chemical and physical methods to the novel diterpene, bertyadionol.

The field-ion contrast exhibited by the pair of stoichiometric ordered compounds Ni 2 Cr and Ni 2 V has been analysed as a preliminary to the metallurgical investigation of these materials. It is shown how the multidomain images from the Ni 2 Cr alloy, and the single domain images from the Ni 2 V alloy, are related to the crystallography of the orthorhombic superlattices. It is found that the chromium atoms are the only contributors to the Ni 2 Cr image, but that nickel is the predominant imaging species for the Ni 2 V alloy. The contrast mechanism cannot be unambiguously determined for these structures, but for the case of the Ni 2 V alloy the relative stabilities of nickel atoms in different atomic environments is discussed in terms of their relative bond energies.

The energy level dispersion, along the chain wave vector, of infrared-active methylene rocking modes has been measured as a function of pressure to 40 kbar for a number of polymethylenes. They are crystalline polyethylene and n-paraffins C23H48, C24H50, C28H58, and C29H60. The crystalline factor-group splitting of each chain mode is observed at various pressures, for those polymethylenes which have orthorhombic or monoclinic structures. The effects of crystal structure, intermolecular force field and intramolecular force field on the observed energy levels as well as on the crystalline factor-group splittings are discussed A hydrogen–hydrogen nonbonded repulsion potential has been calculated as a function of interatomic distance rH••H for 2.3 A < rH••H < 3.0 A from the observed volume dependence of the factor-group splittings of methylene rocking modes. It is shown that the dynamic potential wells along the normal coordinates of the rocking modes are harmonic up to room temperature.

The crystal structures of the 1:1 complexes of inosine 5′-phosphate with cobalt (C10H11O8N4PCo,7H2O) and inosine 5′-phosphate with nickel(C10H11O8N4PNi,7H2O) have been determined from single-crystal X-ray data collected on an automated diffractometer. The both isomorphous crystals belong to orthorhombic system, space group P212121 with four formula units in the unit cell of dimensions a=10.859, b=25.987, c=6.845 A for the cobalt complex and a=10.812, b=25.898, c=6.845 A for the nickel complex respectively. The structure of the cobalt complex was determined by three-dimensional Patterson and Fourier methods and that of the nickel complex was elucidated from that of the cobalt complex. Both were refined by the block-diagonal least-squares method including anisotropic temperature factors. The final R values were 0.051 and 0.075 for the cobalt and nickel complexes, respectively. All of the 25 hydrogen atoms in the case of the cobalt complex and 22 hydrogen atoms in the case of the nickel complex were found. T...

Single crystals of K2SO4 have been prepared taking special precautions to fabricate specimens with 100, 010, 001 faces, i.e., principal planes for the dielectric constant in the orthorhombic system. Polarized i.r. and Raman experiments were made in order to assign the observed frequencies of the sulfate internal vibration modes to the symmetry species of the D2h16 unit cell. Although i.r. transmission was useful for the weak i.r. modes ν1 and ν2 which are forbidden in the Td molecule but allowed at the Cs sites in the crystal, it was found necessary to employ reflectance techniques to obtain meaningful frequencies for the strong, molecularly allowed ν3 and ν4 modes. An analysis is given of both normal incidence and off-axis experiments. Both the transverse and longitudinal mode frequencies are reported for these intense modes and the molecular dipole derivatives are calculated. From the dipole derivatives found in this manner, a detailed dipole coupling theory is developed, and with the aid of the necessary lattice sums, the multiplet splittings due to the dipole part of the intermolecular coupling are calculated. The calculated splittings are comparable in order of magnitude to the observed ones, but the detailed correlation is quite poor. This is attributed to the neglect of short range forces in the coupling Hamiltonian.

Summary Electronprobe microanalyses are used to determine the degree of nonstoichiometry (n,) of an oxidized titanomagnetite as well as the molefraction (X,) of ulvospinel in solid solution with magnetite. This means that the associated chemical composition can be located on the FeO-Fe,O,-TiO, ternary diagram irrespectively of magnetic properties. Every point in the ternary diagram may be represented by extended spinel co-ordinates (ns, Xs), The same apply to rhombohedra1 (nr, X,) and orthorhombic co-ordinates (no, X,). Consequently, any of the three specified co-ordinate systems may be used to plot the chemical composition of an arbitrary iron-titanium oxide independent of its crystallographic structure. The effect of impurities is discussed. While the X-parameter depends on the distribution of impurities between iron and titanium positions, the n-parameter does not and can unambiguously be estimated from the amount of metallic ions present. As this may be obtained by the electronprobe technique on microscopic phases, the method becomes particularly useful to deal with naturally occurring iron-titanium phases. It provides a new way to study the effects of oxidation and form the basis of a procedure to test the phase uniformity of optically homogeneous cation deficient spinels.

The crystal and molecular structures of the fac- and mer-trans- isomers of bromotricarbonylbis(dimethoxyphenylphosphine)manganese(I), [Mn(CO) 3 {P(OMe) 2 Ph} 2 Br], have been determined by single-crystal X-ray diffraction techniques. The fac -isomer crystallizes in the orthorhombic system, space group P 2 1 2 1 2 1 , a = 17.19(2), b = 16.71(2), c = 8.27(1) A, Z = 4. Anisotropic refinement by full-matrix least-squares methods gives R = 0.041. The trans -isomer crystallizes in the monoclinic system, space group P 2 1 / n , a = 14.94(2), b = 24.94(3), c = 13.34(1) A, β = 109.6(2) ° , Z = 8. One of the two independent molecules in the asymmetric unit exhibits disorder of the bromine atom. Isotropic refinement by full-matrix least-squares methods gives R = 0.116. Intensity data were collected on an automatic diffractometer in both cases. Both structures exhibit slightly distorted octahedral geometry about the manganese with one bromine, two phosphorus and three carbon atoms occupying the coordinate positions. A significant structural trans - effect of the carbonyl groups paralleling the known [1] strong carbonyl kinetic trans -effect was not observed.

The i.r. and Raman spectra of tetragonal (red) and PbO and orthorhombic (yellow) PbO have been obtained. Frequencies, in good agreement with those observed, have been calculated using the Wilson FG matrix method. In both forms of PbO, it was found necessary to include metal-metal interactions in order to obtain such agreement. The absence of coincidences between the i.r. and Raman spectra of yellow PbO support the conclusion, reached by neutron deffraction studies, that, the space group of yellow PbO is the centrosymmetric D 2 h 11 ( Pbcm ); thus this material cannot be ferroelectric, as has previously been suggested.

The oxygen rich corner of the ZrO2-WO3-WO2 system has been studied by means of x-ray powder diffraction and electron microscopy at room temperature of specimens quenched from the preparation temperatures of 1000°C and 1100°C. Zirconium tungsten bronzes of formula ZrxWO3 are formed for 0

The vanishing exponential method is used to calculate the electrostatic potential of a rectangular crystalline slab composed of a finite, regular array of similar point charges, each charge occupying a lattice site of an orthorhombic bravais lattice. The results are used to discuss (a) the behaviour of the potential at and near the slab surface, (b) the potential of an electrically neutral crystal, (c) the relationship between the space averaged microscopic potential of (b) and the macroscopic potential and (d) the limiting case of an electrically neutral infinite slab. It is also proved for this slab system, that the limit in the vanishing exponential method does not in general commute with limit used to define an infinite crystal.

The compound Fe2(CO)5(HC2But)3(CO), obtained from Fe3(CO)12 and HC2But was studied by means of X-ray, Mossbauer and 1H nmr techniques. A comparison is made with the already known Fe2(CO)5 (HC2Ph)3(CO) from which the effect of the substituents of the acetylene on the structures is evidenced. Both the compounds show unusual low field absorptions at the 1H nmr and a low temperature run also shows the fluxionality of a But group. The compound crystallizes as orthorhombic prisms, space group Pbca; 3869 indipendent reflexions were measured and 2474 used in the crystal analysis, and the structure was refined to a R factor of 3,9%. It shows two differently surrounded iron atoms, and a complex organic moiety constituted by three acetylene molecules and a ketonic group.

Californium oxysulfate (Cf2O2SO4) has been prepared by calcination of Cf(III)-loaded Dowex resin beads or hydrated Cf2(SO4)3 in air at 700–800°C. At temperatures above 860°C, the oxysulfate decomposed to the sesquioxide. Calcination of the hydrated californium sulfate or the californium oxysulfate salt in atmospheres containing hydrogen, or in vacuum, at 800°C produced the oxysulfide (Cf2O2S). It was observed that the californium oxysulfide could be reoxidized to the oxysulfate by reheating the former product in air at 800°C. The decomposition of the oxysulfate and the oxysulfide to the sesquioxide by heating in air was found to be dependent on both the duration and the temperature of the calcination process. Examination of oxysulfate samples stored at ambient temperatures as a function of time showed that self-irradiation initially causes a loss in crystallinity and subsequently a partial decomposition to the sesquioxide. Lattice parameters for the oxysulfate and oxysulfide were derived from X-ray data. The lattice constants for the orthorhombic oxysulfate are: a 0 = 4·187 ± 0·002 A , b 0 = 4·072 ± 0·002 A and c 0 = 13·009 ± 0·006 A . The cell dimensions for the trigonal oxysulfide are: a 0 = 3844 ± 0·002 A and c 0 = 6·656 ± 0·004 A .

The crystal structure of the anti-androgen cyproterone acetate (CPA, 6-chloro-17-hydroxy-le,2emethylenepregna-4,6-diene-3,20-dione acetate, C24H2904C1) was determined with the aid of symbolic addition. The steroid crystallized in the orthorhombic space group P212121 with a= 10.757 (2), b= 12.266 (3), e-16.623 (3) A,, and Z=4. A three-dimensional data set was collected with Cu Ke radiation (2= 1.5418 A,) on a Syntex P1 diffractometer to a maximum 20 value of 100 ° employing a 0-20 scan technique. The coordinates of the non-hydrogen atoms and their anisotropic temperature factors were refined in a full matrix least-squares manner to a final R index of 0.054 based on F 2. Bond distances around the cyclopropane ring were shortened, implying an interaction with the carbonyl group in ring A.

The anisotropic expansion coefficients of orthorhombic αPb(N3)2 in the temperature range 102–423 K were determined by a single crystal x‐ray method. The cell parameters and rms deviations at 298.2 K are a = 11.33344[17], b = 16.28277[37], and c = 6.64058[10] A. The linear expansion coefficients change gradually from αa = 5.7 × 10−5, αb = 0.3 × 10−5, and αc = 1.4 × 10−5 K−1 at 112, to αa = 8 × 10−5, αb = 0.4 × 10−5, and αc = 2.0 × 10−5 K−1 at 412 K. The largest expansion is in the a direction, which is perpendicular to sheets of azide ions separated by lead atoms.

The crystal structure of the title compound has been determined from single-crystal X-ray diffractometer data. The crystals are orthorhombic with unit-cell dimensionsa =17.147(3),b = 18.147(3),c = 13.860(3) A, space groupPbca andZ = 8. Full-matrix least-squares refinement, using 2215 independent reflections, has reachedR = 0.040.

Polycrystalline CaMoO3 was prepared by a new method making use of the oxygen stability range, and revealed to have an orthorhombic lattice (a=5.448A, b=7.776A, c=5.582A), metallic conduction and Pauli paramagnetism. The results indicate that 4d2 electrons of Mo4+ are delocalized in CaMoO3 as same as those in BaMoO3 and SrMoO3.

Thin lead oxide layers (30−80 A thick) %were grown on evaporated lead films using both thermal oxidation and rf oxygen plasma oxidation. These layers were characterized structurally, using x−ray diffraction in the standard Bragg−Brentano configuration. The layers were crystalline orthorhombic PbO with a very strongly preferred (001) orientation parallel to the {111} preferred orientation in the evaporated Pb films. Thickness and strain were determined from line broadening and peak shift, and the strain as a function of thickness is explained using a simple dislocation model for the structure of the lead−lead oxide interface. The high−temperature orthorhomic phase observed may be stabilized by epitaxial forces.

Die Chalkogenomolybdate und -wolframate (NH4)2MoS3Se (NH4)2MoS2Se2, (NH4)2MoSSe3, (NH4)2WSSe3, Cs2MoS3Se, Cs2MoS2Se2, Cs2MoSSe3, Cs2WSSe3 sowie Cs2MoOS2Se, Cs2WOS2Se, Cs2MoOSSe2 und Cs2WOSSe2 werden rontgenkristallographisch untersucht. Alle Verbindungen kristallisieren rhombisch in der Raumgruppe DPnma im β-K2SO4-Typ. Systematische Beziehungen zwischen den Gitterkonstanten und der Besetzung der Punktlagen in der Elementarzelle werden diskutiert. X-Ray Investigations and Structure Chemistry of Chalkogenomolybdates and -tungstates. II. The chalkogenomolybdates and -tungstates (NH4)2MoS3Se, (NH4)2MoS2Se2, (NH4)2MoSSe3, (NH4)2WSSe3, Cs2MoS2Se, Cs2MoS2Se, Cs2MoSSe3, Cs2WSSe3, Cs2MoOS2Se, Cs2WOS2Se, Cs2MoOSSe2, and Cs2WOSSe2 are investigated by means of X-ray powder diffractometry. All compounds crystallize orthorhombic in spacegroup DPnma and are isomorphous with β-K2SO4. Systematic relations between lattice constants and occupation of atomic positions in the unit cell are discussed.

The Raman spectrum of polycrystalline cyclopropane between 3200 and 10 cm −1 has been recorded. All Raman active fundamentals, two other fundamentals ν 4 ( A ″ 1 ) and ν 7 ( A ″ 2 ), several new crystal components of fundamentals, and many new bands arising from overtones and combinations have been observed. The splittings of the fundamentals, together with the coincidences of infrared and Raman wavenumbers for both fundamentals and lattice modes, are consistent with a C 2 v factor group, a C s site, and two molecules per orthorhombic unit cell.

Extended-chain high-density polyethylene prepared through crystallization at high pressure is substantially stiffer and somewhat stronger than normal folded-chain HDPE. With weight-average molecular weight in the range normal for molding or extrusion resins, the extended-chain material is inductile and brittle; but with molecular weight near 2,000,000, the resin can be rigid and tough. This rigid, tough material can be converted to articles through some of the solid-state processes developed for metals. The volume–temperature behavior of HDPE at 5000 atmospheres appears to reflect a polymorphic transition between orthorhombic and triclinic phases.

The trivalent rare earth sulfides (La to Gd, Eu excepted), combine with US2 and give Ln2US5 orthorhombic sulfides, spatial group Pnma, U3S5-type. The crystal structure of SmIII2US5 is established from single crystals determinations (R = 0,05) : the atomic positions are identical to those of U3S5. These compounds form continuous solid solutions with U3S5 by substitution of LnIII by UIII, and partial solid solutions with US2 by a mechanism involving substitution of LnIII by UIV and vacancies. The two compounds EuIIU2S5 and SmIIU2S5 are isostructural with the preceding ones, from a single crystal study. A continuous passage from SmIII2US5 to SmIIU2S5 and to U3S5 is observed.

Single crystals of β alumina doped with manganese ions have been prepared by high frequency induction melting and slow cooling, followed by Na + - Mn 2+ exchange in molten MnCl 2 . EPR study shows that Mn 2+ ions occupy two kinds of sites. The first one, with an axial zero field tensor corresponds to the tetrahedral positions in the spinel blocks, close to the sodium planes. This seem to indicate that aluminium vacancies in β alumina are partly located in this site. The other, with an orthorhombic zero field tensor, and high D and E values, belongs to the conduction planes.

Acetylene-d2 (CzDz) has two solid phases. The crystal structure of the low-temperature phase has been determined at 4.2 K by neutron powder diffraction. The structure is orthorhombic, with a = 6.193 (3), b = 6.005 (3), c= 5"551 (3) A, space group Acam, Z= 4. The linear molecules lie in layers parallel to (001) in slightly off-diagonal directions. The final agreement index Rz = 0.071. Bond lengths are C-C = 1-18 (1), C-D = 1.06 (2),~. The apparent shortening of the C-C bond compared with the value calculated from highresolution Raman spectra in the gas phase is attributed to the effect of molecular libration.

The EPR spectrum of Cu2+ ions in K2SO4 and Rb2SO4 has been measured in detail at a large number of orientations of the applied magnetic field. Results are in substantial agreement with previously reported work when interpreted using an orthorhombic model. Particular attention has been focused on a detailed fit, covering all orientations, using a more appropriate spin Hamiltonian for arbitrarily low symmetry. An evaluation of the procedure is given and some of the difficulties outlined. The final estimate of off-diagonal elements in the Zeeman and hyperfine tensors is not precise, but they are similar to those required to fit the spectrum of Cu2+ in K2SeO4. A non-coincidence in Zeeman and hyperfine tensor axes of 8 degrees is determined for the xy plane.

The linear electrooptical constants of orthorhombic single crystals of strontium formate, strontium formate dihydrate, and barium formate have been determined for He-Ne LASER radiation at 6328 A…. In order to obtain the absolute signs of the electrooptical constants the chirality of the crystals as characterized by optical activity, morphology, and piezoelectric effects was respected. Electrooptical and piezoelectric constants exhibit a highly anisotropic behaviour, which is connected with the preferential orientation of the strongest ionic bond chains parallel to the [001] axis.Abstract The linear electrooptical constants of orthorhombic single crystals of strontium formate, strontium formate dihydrate, and barium formate have been determined for He-Ne LASER radiation at 6328 A…. In order to obtain the absolute signs of the electrooptical constants the chirality of the crystals as characterized by optical activity, morphology, and piezoelectric effects was respected. Electrooptical and piezoelectric constants exhibit a highly anisotropic behaviour, which is connected with the preferential orientation of the strongest ionic bond chains parallel to the [001] axis.

Neu dargestellt wurden KCoO2 (tetragonal, a = 3,811, c = 7,908 A, c/a = 2,08, Co3+ von 5 O2− koordiniert, Pulverdaten) und RbCoO2 (orthorhombisch, a = 5,656, b = 11,350, c = 16,352 A, isotyp mit KGaO2, Pulverdaten). On KCoO2 and RbCoO2 For the first time prepared were KCoO2 (tetragonal, a = 3.811, c = 7.908 A, c/a = 2.08, C.N. of Co3+ is 5, powder data) and RbCoO2 (orthorhombic, a = 5.656, b = 11.350, c = 16.352 A, isostructural to KGaO2, powder data).

Thallium metavanadate (TIVO3) crystallizes in an orthorhombic lattice (space group Pbcm) with parameters a = 5.16, b = 11.22, c = 5.73 Å with Z = 4. The structure was determined using 255 independent reflections measured with an automatic diffractometer.Vanadium has a tetrahedral coordination in this structure. The tetrahedra are joined by having two oxygens in common to form chains (VO3)nn− parallel to the c axis.TIVO3 is established to be isomorphous to the metavanadates MVO3 (M = K, NH4, Rb, Cs). Thallium has a coordination number of ten analogous to that of the alkali metals. The study demonstrates that the 6s2 doublet of thallium is sterochemically inactive in TIVO3. [Journal translation]

${\mathrm{Li}}_{2}$Ge${\mathrm{O}}_{3}$ is an orthorhombic pyroelectric transparent crystal with space group ${C}_{2v}^{12}(Cmc{2}_{1})$. Scott et al. have shown that it can be grown easily in very large boules by the Czochralski technique. We report and discuss infrared reflectivity and Raman measurements of the lattice vibrational modes along all three polarization directions, and the optic index of refraction. The frequencies of the modes determined from the two techniques are in good agreement with each other except that several more modes are observed by the Raman techniques. The clamped-dielectric-constant values calculated from the modes are in fair agreement with our capacitance measurements.

Three new compounds were prepared in single crystals. They crystallise in the orthorhombic system, space group Pn2Imo or Pnm2I. Their cell edges: TlTaB2O6 a=5×3,86 b=9,50c=7,44 A; RbNbB2O6 a=5×3,94 b=9,49 c=7,42 A; RbTaB2O6 a=5×3,88 b=9,52 c=7,44 A show that they are isotype with TlNbB2O6 and form a new family of double borates with it.

Althausite occurs as cleavable masses in serpentine-magnesite deposits at Modum, Norway. The proposed formula in Mg2PO4 (OH0.37F0.25O0.10)0.81 with partly vacant halide sites. It is orthorhombic, space group Pna21, a = 8.258, b = 14.383, c = 6.054 A, Z = 8. D(meas)=2.97, ϱ(calc) = 2.91 g/cm3 (X-ray), ϱ(calc) = 3.06 g/cm3 (Gladstone-Dale), H = 3 12 −4. The strongest X-ray powder lines (41 given, FeKα radiation) with intensities and indices are 3.593 (100)(040), 3.316 (90)(211), 3.024 (80)(002), 2.786 (60)(112), 2641 (60)(122). The mineral is light grey with vitreous lustre, running brown on alteration to apatite. Non-fluorescent. Perfect cleavage {001}, distinct cleavage {101}. It is biaxial positive, α=1.588, β=1.592, γ=1.598, 2Vγ(calc)=78.5°, negative elongation, X=b, Y=c, Z=a. IR, DTA and TGA data are given.

The thermal expansion of GeSe has been studied above room temperature up to the melting point of 670 plus or minus 5 C by X-ray diffraction techniques using a 190 mm Unicam high temperature camera. The thermal expansion of the crystallographic axes is linear with a distinct change in the expansion coefficients for all axes above 400 C. The relative changes in the axes indicate a rearrangement of the structure towards cubic symmetry with increasing temperature. The transformation of GeSe from the orthorhombic to a normal NaCl-type structure is observed at 651 plus or minus 5 C. The lattice parameter of the cubic form of GeSe is a 0 ? 5.730 plus or minus 0.003 A at 656 C. The GeSe lattice remains cubic up to the melting point.

Expressions for 4R1(I) and 4R(I), which are based on the fourth powers of the discrepancies (IN -- IcP/σ21) and (IN - IcP) respectively, are worked out for the case of a crystal and model satisfying the requirements of the Wilson distributions. A comparative study of 4R1(I) and 4R(I) is carried out to see whether the concept of a normalized index is useful. Since 4R1(I) is found to be better, it is also compared with BR1(I). As 4R1(I) could be useful in the initial stages of the structure completion process, general expressions for this index for the related and unrelated types of models of triclinic, monoclinic and orthorhombic crystals containing any number and types of atoms at general positions in the asymmetric unit are obtained.

The positional parameters in the orthorhombic phase of solid tungsten hexafluoride WF$sub 6$, have been determined by total profile analysis of a neutron powder pattern taken at 193$sup 0$K. WF$sub 6$ at 193$sup 0$K is orthorhombic, with space group Pnma(D$sup 16$/sub 2h/) and a = 9.603(3), b = 8.713(4), and c = 5.044(3) A at 193$sup 0$K. The full matrix, least-squares refinement converged at R = $Sigma$ (parallel y$sub 0$ - (1/c)y/sub c/parallel)/ $Sigma$ y$sub 0$ = 0.075 where c is the scale factor and y$sub 0$ is one of the 306 background-corrected intensities in range of one or more Bragg reflections along the pattern. The refinement showed that, at this temperature, WF$sub 6$ has the orthorhombic UF$sub 6$ structure. The mean W--F distance is 1.81 A, and the mean F--F separation between octahedra is 3.12 A. The results are compared with previous neutron profile studies of the orthorhombic phases of UF$sub 6$ and MoF$sub 6$ at 193$sup 0$K, and with a neutron profile Kubic Harmonic analysis of the cubic form of WF$sub 6$ at 266$sup 0$K. On the basis of these structural studies in this series of hexafluorides, reasons are given why MoF$sub 6$ and WF$sub 6$ have amore » high-temperature cubic phase, but UF$sub 6$ does not. Deviations from idealized hcp coordinates in the orthorhombic phases are in a direction such that the fluorine atoms become strongly bonded to the metal atoms to form a molecular, rather than an ionic, lattice.« less

A series of MV2O6 compounds with M = Ni, Mg, Co, Zn, Mn, and Cd having the orthorhombic columbite-type structure has been prepared at pressures of 50–80 kbar and temperatures of 800–1200°C. CuV2O6II was found to have a monoclinic distortion with probable space group P21/c and a = 4.824(1), b = 13.483(2), c = 5.652(1)A˚and β = 91.02(2). The transition from the brannerite to columbite-type structures involves an increase of V5+ coordination from 5 + 1 → 6, a change in oxygen packing from cubic close-packed to hexagonal close-packed, a retention of part of the structure of the VO6 sheets and a collapse of the MO6 rutile-like chanins into αPbO2 chains. The relative stabilities of the trirutile, columbite, and PbSb2O6 structures are discussed in terms of electrostatic repulsion forces, polarization, and covalency. It is concluded that minimization of cation-cation repulsion for d10 ions cannot be responsible for the stability of the trirutile structure, since the d10 ions As5+ and Sb5+ are frequently found in the PbSb2O6 structure in which each Sb5+ or As5+ ion has 3 Sb5+ or As5+ neighbors. In plots of rM3 vs unit cell volumes for MV2O6 and MNb2O6 compounds, the volume of the Mg-containing compound always lies above the line connecting the other compositions. This deviation is attributed to the relatively greater covalence and consequent shortening of M O bonds where M = Ni, Co, Zn, Mn, and Cd.

The crystal structure of a nickelahexakis(trifluoromethyl)cycloheptatriene, C18H18F18NiO6P2 has been determined. The compound crystallizes in the orthorhombic space groupPbcn, witha = 17.355(5),b = 11.014(3),c = 15.026(5) A andZ = 4. The molecular symmetry is 2(C2). X-ray intensity data were collected by counter methods, using MoKα radiation, and least-squares refinement led toR = 0.050 for the 804 reflexions for which. ¦F0¦2 >2σ(¦F0¦2). The [C2(CF3)2]3 ligand is attached to the nickel atom by σ-bonds from the two terminal carbon atoms (Ni—C = 1.96 A) and by a η-bond from the two central (double-bonded) carbon atoms (Ni—C = 2.04 A). This is the first example of the coordination to a transition metal of an olefinic group which is also part of a chelate.

The carbene complex trans-[CH3(CH2 COCH2 CH2)Pt{P(CH3)2 C6 H5}2]PF6 crystallizes in the centrosymetric orthorhombic space group Pcca (D82h) with a = 15.503(7), b = 18.81(1), c = 17.66(1) A. The measured density of 1.81(1) g cm−3 agrees with d(calc) = 1.81 g cm−3 for M = 703.41 and Z = 8. Three dimensional X-ray diffraction data were collected on an automatic four circle diffractometer using Mo radiation. The structure was solved by a combination of Patterson, Fourier and least-squares refinement techniques. The final conventional agreement factor for the converged model is R1 = 0.044, calculated on 1763 observations for which I > 3σ(I), with 160 variables. The anion lies on a crystallographic two-fold axis of symmetry, and is disordered. The coordination geometry is essentially square planar about the platinum atom. The cyclic carbene ligand is almost planar and is coordinated approximately perpendicular to the Pt square plane. The mean PtP distance is 2.305(5), the PtC(sp3) bond length is 2.080(18) and the C(sp2) atom lies 2.00(2) A away from the platinum atom. The structure is discussed in terms of the trans-influences of the ligands, and the character of the PtC(sp2) bond.

The crystal structure of triphenylborane has been determined. The compound crystallizes in the orthorhombic space group Pbcn with Z = 4 and a = 17.265, b = 10.355, c = 8.03 A. In contrast to triphenylgallium and triphenylindium which belong to the same space group and have similar cell dimensions, no intermolecular interactions are found for the title-compound. The phenyl groups are tilted by about 30° with respect to the boron valence plane.

Some physical and mechanical properties of U-Ru alloys containing 0.05–6 at.% Ru have been investigated in the as-cast and oil-quenched conditions, from 900°C and 720°C. The properties investigated were thermal expansion, crystalline lattice parameters, density and microhardness. As the Ru content increased, the coefficient of dilatation decreased in a manner depending upon the temperature. For the as-cast alloys, the orthorhombic lattice parameters of α-uranium, a , b , and c , decreased as the Ru content increased. For the alloys quenched from 900°C, the b parameter decreased and the a and c parameters increased with Ru content. These changes caused distortion in the unit cell by comparison with the as-cast condition, and produced X-ray line broadening. In the case of alloys quenched from 720°C, the a parameter was not significantly influenced, the b parameter was decreased, and the c parameter increased. The distortion in this case was insufficient to cause line broadening. In the as-cast alloys, the density decreased and the microhardness increased as the Ru content increased. The density of alloys quenched from 720°C was slightly higher than that of the as-cast alloys. Quenching from 900°C produced a greater increase in density than quenching from 720°C. The hardness values of alloys quenched from 720°C were slightly higher than those of the as-cast alloys. Quenching from 900°C produced considerable strengthening, particularly in the high Ru-content alloys.

Na2MoO4·2H2O is orthorhombic, with the space group of Pbca and with cell constants of a=8.463(3), b=10.552(3), and c=13.827(6) A; U=1234.8 A3; Z=8. The crystals are composed of alternate layers of MoO42− tetrahedra and water molecules. The layers are connected by interlinking sodium cations and hydrogen bonds. The MoO42− tetrahedron is slightly elongated in the direction of the hydrogen bonds.

The organometallic derivatives [Co(π-C5H5)(C4F6)2PO(OH)](1) and [Mn(CO)3(C4F6)2SC6F5](2) which resulted from the interaction of hexafluorobut-2-yne with metal complexes have been studied by X-ray diffraction and shown to contain non-planar (CF3)4C4X heterocycles with non-bonding metal–heteroatom separations. The absence of an Mn–S bond in (2) leads to the formulation of a zwitterion structure formally involving a sulphonium derivative with a Mn(–1) species. Crystals of (1) are orthorhombic with a= 9·353(7), b= 9·893(7), c= 17·923(10)A, space group P212121, and Z= 4. Crystals of (2) are triclinic with a= 7·889(6), 6=11·737(8), c= 12·195(9)A, α= 91·45(10), β= 69·71(10), γ= 81·55(9)°, space group P and Z= 2. Intensity data were collected on a four-circle diffractometer, and the structures solved by Fourier methods; least-squares refinements converged at R 6·3% over 1922 reflections for (1) and 4·5% over 3229 reflections for (2).

Inelastic neutron scattering measurements on single-domain orthorhombic KNbO3 at room temperature show no evidence of overdamped scattering, in contrast with previous neutron results in the cubic phase. As in the case of KTaO3, the observed diffuse x-ray planes are shown to correspond to a highly anisotropic transverse acoustic branch with an unusually flat dispersion in the 'soft' plane. In addition, a well defined optic branch with a polarization related to the orthorhombic-rhombohedral phase transition is seen to become soft as q to 0 in the soft plane. A mode-eigenvector determination confirms the x-ray result that essentially only one atom (niobium) moves in the flat transverse acoustic mode. The connection with other experimental results and with the independent chain model is discussed.

Crystals of LiH(CsH404). 2H20 are orthorhombic (space group Pnma) with a = 16.837 (2), b = 6.822 (1), c= 8.198 (2) A, Z=4, Q= 1.4677 gcm -3. The crystal structure was determined by Patterson syntheses. Full-matrix least-squares refinement with anisotropic temperature parameters for the non-hydrogen atoms converged to an R index of 0.040. The hydrogen phthalate ion is found to be planar. The carboxyl groups are linked by an extraordinarily short intramolecular hydrogen bond (2.385 A). The Li ion is found in tetrahedral coordination.

The crystal structure of polyisobutylene was determined by x-ray analysis. The orthorhombic cell, with a = 6.88 A, b = 11.91 A, c (fiber axis) = 18.60 A (space group: P212121 − D), contains two molecular chains each consisting of eight monomeric units in the fiber identity period. The chain conformation is essentially an (8/3) helix, but deviates appreciably from the exact (8/3) helix symmetry. The symmetry of the molecular chain is only a twofold screw axis in exact sense, and a crystallographic asymmetric unit consists of four monomeric units. The torsional angles are where M denotes the methyl group. The averaged skeletal CCH2C and CCM2C bond angles are 128° and 110°, respectively. The large CCH2C bond angles may be due to steric respulsion between the adjacent methyl groups, giving intramolecular distances larger than 3.09 A.

A series of nickel(0)—stilbene complexes has been prepared by the reaction of triarylphosphines or tert-butyl isocyanide with bis(1,5-cyclooctadiene)nickel(0) in hexane. The structure of the complex bis(tri-p-tolylphosphine)(trans-stilbene)nickel(0) hemitetrahydrofuranate, Ni[P(C6H4CH3)3]2[(C6H5)HCCH(C6H5)] · 0.5(C4H8O), has been determined at room temperature from three-dimensional X-ray data collected by counter methods. The structure has been refined by least-squares techniques to a final R index (on F) of 0.092 based on 2417 observations above background. The material crystallizes in the orthorhombic space group D102h-Pccn, with eight molecules of complex and four molecules of solvent in a cell of dimensions a = 19.548(8), b = 26.145(12), c = 19.718(9) ». The Ni atom has trigonal coordination if the olefin is regarded as a monodentate ligand. The five atoms of the inner coordination sphere are distorted planar and the two olefinic carbon atoms are essentially equidistant from the nickel atom. The structure is compared with that of bis(tri-p-tolylphosphine)(azobenzene)nickel(0) determined previously. Observed differences in the bonding of the olefin and the isoelectronic azo complex are discussed.

Neutron diffraction studies on polycrystalline UF6 have been carried out at 1930K and 2930K. At both temperatures, UF6 is orthorhombic with the space group Pnma (D162h) and Z = 4. Measured lattice parameters are a = 9.924 (10) A, b = 8.954 (9) A, c = 5.198 (5) A at 2930K and a = 9.843 (11), b = 8.920 (10), c = 5.173 (6) A at 1930K. The neutron diffraction patterns were analyzed by the least-squares profile- fitting technique. On cooling, the hexagonal close-packing tends to become more regular, and the F-F distances external to a UF6 octahedron contract. The octahedra are nearly regular with a mean U--F distance of 1.98 A, a mean F--F edge of 2.80 A, and a F--U--F angle of 90.00 at 1930K.