Showing papers in "Zeitschrift für Naturforschung A in 1998"
TL;DR: In this article, the authors show that the expansion series in the usual Painleve analysis is resummable in some different ways, using a simple truncated expansion with a quite universal reduction function.
Abstract: To study a nonlinear partial differential equation (PDE), the Painleve expansion developed by Weiss, Tabor and Carnevale (WTC) is one of the most powerful methods In this paper, using any singular manifold, the expansion series in the usual Painleve analysis is shown to be resummable in some different ways A simple nonstandard truncated expansion with a quite universal reduction function is used for many nonlinear integrable and nonintegrable PDEs such as the Burgers, Korteweg de-Vries (KdV), Kadomtsev-Petviashvli (KP), Caudrey-Dodd-GibbonSawada-Kortera (CDGSK), Nonlinear Schrodinger (NLS), Davey-Stewartson (DS), Broer-Kaup (BK), KdV-Burgers (KdVB), , sine-Gordon (sG) etc
92 citations
TL;DR: Amorphous Si37C32N31 and Si37c29N34 ceramics were produced by pyrolysis of a polyhydromethylsilazane precursor and their structure was investigated by X-ray and neutron diffraction.
Abstract: Amorphous Si37C32N31 and Si37C29N34 ceramics were produced by pyrolysis of a polyhydromethylsilazane precursor. Their structure was investigated by X-ray and neutron diffraction. Wide angle diffraction showed that the Si-atoms are preferentially bonded to nitrogen atoms, but also bonding to carbon atoms was found. This suggests that the excess carbon atoms form an amorphous graphite-like phase. Small angle scattering revealed that the ceramics are inhomogeneous. The evolution of the phase separation during annealing was investigated and it was concluded that amorphous Si3N4 precipitates grow in the Si-C-N materials. The results are compared with previous results for amorphous Si24C43N33 produced from a polysilylcarbodiimide precursor [1 3].
37 citations
TL;DR: In this article, the P-O-P angle distribution in the PO4 tetrahedron with corner-linked PO4 units has been determined by using the present X-ray diffraction experiments.
Abstract: Abstract Recently, the lengths of the two P-O bonds in the PO4 tetrahedron were obtained by neutron diffraction of high real-space resolution. By use of the present X-ray diffraction experiments, the P-P distance belonging to pairs of corner-linked PO4 units is determined. Using this length of (294 ± 2) pm and taking into account the P-0 bond distance to the bridging oxygen atom of 158 pm, a mean P-O-P angle of 137° ± 3° is calculated. The reverse Monte Carlo simulations fit the neutron and X-ray structure factors. The P-O-P angle distribution obtained this way possesses a mean angle of 141°. An interpretation of the first scattering peaks is presented by analysing the occupancy and the distances of various co-ordination shells by use of model configurations. The low occupancy of the first shells allows the application of the schematic hole model of Dixmier. The first X-ray diffraction peak at 13 nm-1 is related to the P-P2nd shell, the shoulder at 20 nm-1 arises from the P-O2nd shell. The most similar crystalline structure with vitreous P2O5 is the orthorhombic P2O5, form II. But it has more effectively orientated terminal oxygen atoms and, thus, a higher packing than the glass.
29 citations
TL;DR: In this article, the temperature evolution of the Li NMR spectra and relaxation rates in many investigated solid lithium conductors shows more or less the same behavior and the mean nuclear quadrupole coupling parameters reduce by either about 5 or by a factor of 15 in all the compounds.
Abstract: The temperature evolution of the Li NMR spectra and relaxation rates in many investigated solid lithium conductors shows more or less the same behavior. These compounds are characterized by a disordered lithium sublattice with a surplus of cation sites in cavities and channels of the anionic network. At low temperature, the spectra consist of a central line and a distributed satellite base structure. Upon increasing temperature, both components narrow until a reduced constant width with a well resolved quadrupole structure is reached. The mean nuclear quadrupole coupling parameters reduce by either about 5 or by a factor of 15 in all the compounds. The spin-lattice relaxation rates 1/T 1 are asymmetric as a function of reciprocal temperature and of quadrupolar origin. The activation energy of the main process of ionic motion may best be obtained from the temperature dependence of the dipolar spin-spin-relaxation rate 1/T2. The spectral densities of the relaxation dependences correspond to those for inhomogeneous motions; they may be described by modification of the BPP equation, a Cole-Davidson distribution or a Kohlrausch-Williams-Watts function. Within this study three LISICON systems, Li4 3xGaxGeO4, and two phosphates Li3M2(PO4)3 (M = Sc, In) were investigated or re-investigated which fit well into this scheme. Activation energies of 39 43 kJ/mol (Li4 3xGaxGeO4 with x = 0.06, 0.14, 0.24), 53 kJ/mol (Li3Sc2(PO4)3) and 75 kJ/mol (Li3In2(PO4)3) were obtained.
21 citations
TL;DR: In this paper, some analogues of the nonlinear optical crystal L-arginine phosphate monohydrate (LAP) were obtained and investigated by means of IR, NQR, X-ray diffraction and SHG methods.
Abstract: Abstract Some new analogues of the nonlinear optical crystal L-arginine phosphate monohydrate (LAP) (Arg • HIO3 , Arg • 2HIO3 , Lys • HIO3 , Lys • 2HIO3 , Lys • 3HIO3 , Bet • 3HIO3) were obtained and investigated by means of IR, NQR, X-ray diffraction and SHG methods. The importance of this class of crystals for revealing new nonlinear optical crystals is pointed out.
20 citations
TL;DR: In this paper, the rotational B constants of the rare gas -spherical top van der Waals complexes Ar-CH4 and Kr-Ch4 were measured in the wavelength region near 1310 cm-1 and assigned.
Abstract: Abstract Diode laser spectra of the rare gas - spherical top van der Waals complexes Ar-CH4 and Kr-CH4 were measured in the wavelength region near 1310 cm-1 and assigned. The most prominent lines of both complexes exhibit three dense but well resolved RP0, QR0, and RQ0 branches, correlated to the R(0) transition of the triply degenerate bending vibration v4 of methane, CH4. A model Hamiltonian based on Coriolis coupled states was applied for the assignment, analysis and fitting of the spectra to within the experimental accuracy of ≈ 15 MHz. The rotational B constants of the upper and lower states determined from the three allowed branches appeared to be strongly correlated. The precision in the determination of the rotational B constants of the two complexes was substantially increased by additional recording of several weak transitions in the nearly forbidden QP0 and RR0 branches, which were fitted together with the allowed transitions. The separation between the rare gas atom and the methane molecule in the ground vibrational state was determined to be 3.999 Å and 4.094 Å for Ar-CH4 and Kr-CH4, respectively. The measured small values of the splitting between the K=0 and the K = ±1 levels in the vibrationally excited state (0.39 cm-1 and 0.67 cm-1 for Ar-CH4 and Kr-CH4, respectively), which characterizes the anisotropy of the intermolecular potential, indicated that Kr-CH4 and Ar-CH4 together with Ne-SiH4 represent examples close to the free rotor limit, where the spherical top CH4 is almost free to rotate within the complex. In comparison, the previously analyzed Ar-SiH4 van der Waals molecule is closer to the hindered rotor limit.
18 citations
TL;DR: In this article, the entropy change at phase transitions was separated into a volume-dependent part and configurational part, and the molar volumes along the nematic-isotropic phase transition TNl(p) were determined for the liquid crystalline, isotropic and also for the crystal phases.
Abstract: Abstract P, Vm , T data were established for 4'-n-hexyl-biphenyl-4-carbonitrile (6CB) and 4'-n-heptyl-biphenyl-4-carbonitrile (7CB) between 300 and 370 K up to 300 MPa, and specific volumes were determined for the liquid crystalline, isotropic, and also partly for the crystal phases. Volume and enthalpy changes at the phase transitions are also presented. In the case of 6CB, a new crystal phase has been detected, corresponding to a triple point at 338 K and 196 MPa. The p, Vm , T data enabled us to separate the entropy change into a volume-dependent part and configurational part. From the molar volumes along the nematic-isotropic phase transition TNl(p), the molecular field parameter γ=∂lnTNI/∂lnVNI was determined.
17 citations
TL;DR: In this paper, it was shown that some of the experiments allegedly proving the reality of relativistic length contraction and time dilation can be unambiguously interpreted as manifestations of velocity-dependent dynamical interactions taking place within the systems involved in the experiments.
Abstract: Abstract Recent advances in the theory of electromagnetic retardation have made it possible to derive the basic equations of the special relativity theory and to duplicate the most important practical results of this theory without using the concepts of relativistic length contraction and time dilation. Thus the reality of these concepts appears to be questionable. It is imperative therefore to reexamine the experimental evidence supporting these concepts. The calculations presented in this paper show that some of the experiments allegedly proving the reality of length contraction and time dilation can be unambiguously interpreted as manifestations of velocity-dependent dynamical interactions taking place within the systems involved in the experiments rather than as manifestations of length contraction or time dilation.
16 citations
TL;DR: In this paper, the volume changes and the slopes of the transition lines were measured for the smectic, nematic and isotropic phases of 4'-n-octyl-biphen-yl-4-carbonitrile (8CB) in the temperature range 300-370 K and pressures up to 300 MPa.
Abstract: Abstract P, Vm , Tdata have been measured for the smectic, nematic and isotropic phases of 4'-n-octyl-biphen-yl-4-carbonitrile (8CB) in the temperature range 300-370 K and pressures up to 300 MPa. At atmospheric pressure all phase transitions appear to be of first order due to a discontinuity in the density. The volume change at the smectic A -nematic transition is only a tenth of the volume change at the clearing temperature. At moderate pressures below 80 MPa the SA -N transition could be detected as a discontinuity in the period of oscillation in measurements with a high-pressure vibrating tube densimeter. At higher pressures the discontinuity seems to die away, possibly indicating a change from first order to second order transition. From the volume changes and the slopes of the transition lines we calculate the enthalpy changes at the phase transition. The p, Vm , T data enable us to calculate the volume part of the entropy and the molecular field parameter γ=δln TNI/δln VNI .
16 citations
TL;DR: In this article, a large number of solid fluoride and heteroligand acidocomplex compounds of antimony(III) and bismuth (III) with single and mixed cations have been prepared from aqueous solutions.
Abstract: Abstract A large number of solid fluoride and heteroligand acidocomplex compounds of antimony(III) and bismuth(III) with single and mixed cations has been prepared from aqueous solutions. Their crystal structures and 121,123Sb and 209Bi NQR spectra have been investigated in a wide temperature range.
16 citations
TL;DR: In this paper, a TGA/DSC and diffractometric (XRD) study has been performed on the solid state reaction system Li2CO3 -Fe2O3 in the x Li range 0.10±0.50.
Abstract: Abstract A thermoanalytical (TGA/DSC) and diffractometric (XRD) study has been performed on the solid state reaction system Li2CO3 -Fe2O3 in the x Li range 0.10±0.50. A detailed analysis of the results shows that the data are in agreement with a reaction model where the carbonate decomposition is regulated by the formation of both LiFeO2 and LiFe5O8 , and the relative amount of the two phases depends on the initial composition. The DSC evidence offers the possibility to directly quantify the LiFe5Ox phase. Furthermore it allows one to obtain the enthalpies of formation of both LiFeO2 and LiFe5O8 .
TL;DR: In this article, a short review on the structure of molten halide systems as revealed by neutron diffraction and computer simulation techniques has been presented, which can help in gaining a better understanding of these systems at the microscopic level.
Abstract: Abstract Much experimental and theoretical effort has gone into revealing the internal complexities of molten salts for the past two decades. In this paper we shall show how neutron diffraction and computer simulation techniques have helped in gaining a better understanding of these systems at the microscopic level. Firstly, a short review on the structure of molten halide systems as revealed by these techniques will be presented. Complementarity of using X-rays with neutrons and, some recent results on the structure of molten DyCl3 obtained by combining neutron and X-ray diffraction with molecular dynamic simulations will be discussed. Neutron diffraction isotopic substitution techniques have played an important role in elucidating the interatomic structure of a diversity of molten salts. Pair distribution functions (PDFs), determined for a number of 1:1 and 2 :1 halide melts, provided theorists with a critical test of their model potentials. It is now clear that for 1:1 molten systems theoretical models based on Fumi-Tosi potentials can adequately describe many of the structural features. Nevertheless, the chal-lenge is two fold: (i) to determine real interatomic potentials for 2:1 and 3 :1 molten systems capable of reproducing not only the microscopic structural details obtained at the partial PDF, gαβ (r) level, but also their macroscopic behaviour and, (ii) to characterise the structure in binary molten salt mixtures.
TL;DR: In this article, the local coordination of europium in vitreous Eu metaphosphate has been investigated, using information obtainable from crystalline EuP3O9.
Abstract: The local coordination of europium in vitreous Eu metaphosphate has been investigated, using information obtainable from crystalline EuP3O9. One glassy sample and one crystalline sample of nominal EuP3O9 composition were examined by X-ray diffraction. The description of the close coordination of Eu, deduced from the orthorhombic structure of the crystalline sample, was used as a model for the amorphous situation. Besides, as a monoclinic form of Eu metaphosphate is also reported to exist, a second model was deduced from this structure, starting from the isomorphous monoclinic Yb metaphosphate. Best fitting calculations indicated that orthorhombic coordination is the better model for the short range order of europium in the vitreous metaphosphate.
TL;DR: In this paper, the superposition principle for non-negative Fourier polynomials was investigated from a Bayesian point of view, and it was shown that it implies wave-mechanical interference already exists for classical probabilities.
Abstract: Quantum mechanics is spectacularly successful on the technical level but the meaning of its rules remains shrouded in mystery even more than seventy years after its inception. Quantum-mechanical probabilities are often considered as fundamentally different from classical probabilities, in disregard of the work of Cox (1946) – and of Schrodinger (1947) – on the foundations of probability theory. One central question concerns the superposition principle, i. e. the need to work with interfering wave functions, the absolute squares of which are probabilities. Other questions concern the relationship between spin and statistics or the collapse of the wave function when new data become available. These questions are reconsidered from the Bayesian point of view. The superposition principle is found to be a consequence of an apparently little-known mathematical theorem for non-negative Fourier polynomials published by Fejer in 1915 that implies wave-mechanical interference already for classical probabilities. Combined with the classical Hamiltonian equations for free and accelerated motion, gauge invariance and particle indistinguishability, it yields all basic quantum features – wave-particle duality, operator calculus, uncertainty relations, Schr odinger equation, CPT invariance and even the spin-statistics relationship – which demystifies quantum mechanics to quite some extent.
TL;DR: In this article, the NQR line shapes of 209Bi in the α-Bi2O3-based mixed oxides were recorded in zero and weak magnetic fields (Hext < 500 Oe) and compared with the results of computer simulation.
Abstract: Abstract The NQR line shapes of 209Bi in the α-Bi2O3-based mixed oxides Bi2O3 • 2M2O3 (M = Al, Ga). Bi2O3 • 3GeO2, and 2Bi2O3 • 3GeO2 are recorded in zero and weak magnetic fields (Hext < 500 Oe) and compared with the results of computer simulation. Splittings and line shape asymmetry, exhibited by the resonances, suggest that internal magnetic fields, similar to those earlier reported for α-Bi2O3 and Bi3O4Br, may exist in these compounds. In the spectra of single crystal Bi4Ge3O12, the line multiplicity in external magnetic fields is higher than simulated, which might results from domains in the crystal. In external magnetic fields a notable increase in the line intensity was observed, the effect depending on the mutual orientation of the EFG axes and the fields perturbing the nuclear spin system.
TL;DR: In this paper, Ott, Grebogi, and Yorke (OGY) control method was used to stabilize the unstable periodic orbits of a chaotic relay system using small variations in the height of the relay output as control input.
Abstract: The control method of Ott, Grebogi, and Yorke (OGY) is used to stabilize the unstable periodic orbits of a chaotic relay system. Small variations in the height of the relay output are used as control input. The influence of the control activation bound is studied in detail via the one-dimensional Poincare map of the controlled system. The reduced sensitivity of the multi-step OGY method for higher period orbits can thus directly be verified.
TL;DR: In this article, the changes of the permittivity maximum with the electric field intensity evidence the first-order character of the ferroelectric phase transition at Tc1, and a method for the determination of the corresponding coefficients is proposed.
Abstract: Abstract Electric permittivity measurments as functions of temperature at constant dc electric field and as functions of the dc electric field at constant temperatures in the paraelectric phase have been performed for DMAGaS crystal. The changes of the permittivity maximum with the electric field intensity evidence the first-order character of the ferroelectric phase transition at Tc1. The field dependence of the permittivity ε(E) in the paraelectric phase is discussed, using the classical electric equation of state. A method for the determination of the corresponding coefficients is proposed. The obtained B and C coefficients, together with double hysteresis loop observed above Tc1 prove the first-order character of the ferroelectric phase transition in DMAGaS crystal.
TL;DR: In this article, the electronic structure of nitrogen atoms as impurities in an ionic TiO2 crystal has been investigated by analyzing electric field gradients (EFGs) measured by use of short-lived β-emitting 12N implant-ed following nuclear reactions.
Abstract: Abstract The electronic structure of nitrogen atoms as impurities in an ionic TiO2 crystal has been investigated by analyzing electric field gradients (EFGs) measured by use of short-lived β-emitting 12N implant-ed following nuclear reactions. Conventional β-NMR and its modification, suitable for the detection of quadrupole effects in the NMR spectra, were used for the investigation of hyperfine interactions of 12N located in substitutional sites of O atoms and interstitial sites in the crystal. In order to deduce absolute values of the EFGs from the obtained eqQ/h, the quadrupole moment of 12N has been determined from the NMR detection of 12N implanted in BN(hexagonal) crystal. Here the EFG at the N atom in BN was measured by detecting the FT-NMR of 14N in the crystal. The EFGs in TiO2 are compared with the theoretical predictions based on the ab initio band-structure calculation in the framework of the KKR method.
TL;DR: In this paper, the role of three-body interactions on the structural and dynamical properties of the solution has been investigated, and the presence of three body corrections leads to the reduction of the first shell coordination number of Ca(II) in liquid ammonia from 9 to 8, the increase of the size of the solvation shell by 0.33 A and the disappearance of the sec-ond solvation shells.
Abstract: Abstract Molecular dynamics simulations have been performed with and without three-body corrections at an average temperature of 240 K using a flexible ammonia model. The system consists of one calcium ion and 215 ammonia molecules. The calcium(II)-ammonia interactions were newly developed, based on ab initio calculations with a basis set of double zeta quality. The role of three-body interactions on the structural and dynamical properties of the solution has been investigated. The presence of three-body corrections leads to the reduction of the first shell coordination number of Ca(II) in liquid ammonia from 9 to 8, the increase of the size of the solvation shell by 0.33 A and the disappearance of the sec-ond solvation shell.
TL;DR: In this paper, the authors investigated several ensembles of artificial and real-world greyscale images to find different invariance properties: translation invariance by determining an average pair-correlation function, scale invariance using the power spectrum and the coarse graining of the images, and a new hierarchical invariance recently proposed.
Abstract: Abstract To answer the question about the way our visual system processes images it has to work with every day, it is necessary to investigate the statistical structure of these pictures. For this purpose we investigated several ensembles of artificial and real-world greyscale images to find different invariance properties: translation invariance by determining an average pair-correlation function, scale invariance by investigating the power spectrum and the coarse graining of the images, and a new hierarchical invariance recently proposed [D. L. Ruderman, Network 5, 517 (1994)]. The results of our work indicated that the assumption of translational invariance can be taken for granted. Our results concerning the scale invariance are qualitatively the same as those found by Ruderman and others. The deviations of the distributions of the logarithmically transformed images from a Gaussian distribution cannot be seen as clearly as stated by Ruderman. This results from the fact that for a correct determination of the deviations the non-linear transformation must be considered. Depending on the preprocessing of the images the results concerning the hierarchical invariance differed widely. It seems that this new invariance can be confirmed only for logarithmically transformed images.
TL;DR: In this article, the authors analyzed the nonlinear propagation of waves on the interface between two superposed dielectric fluids with uniform depths in the presence of a normal electric field, taking into account the interfacial surface charges.
Abstract: Abstract The method of multiple scales is used to analyse the nonlinear propagation of waves on the interface between two superposed dielectric fluids with uniform depths in the presence of a normal electric field, taking into account the interfacial surface charges. The evolution of the amplitude for travelling waves is governed by a nonlinear Schrödinger equation which gives the criterion for modulational instability. Numerical results are given in graphical form, and some limiting cases are recovered. Three cases, in the pure hydrodynamical case, depending on whether the depth of the lower fluid is equal to or greater than or smaller than the one of the upper fluid are considered, and the effect of the electric field on the stability regions is determined. It is found that the effect of the electric field is the same in all the cases for small values of the field, and there is a value of the electric field after which the effect differs from case to case. It is also found that the effect of the electric field is stronger in the case where the depth of the lower fluid is larger than the one of the upper fluid. On the other hand, the evolution of the am-plitude for standing waves near the cut-off wavenumber is governed by another type of nonlinear Schrödinger equation with the roles of time and space are interchanged. This equation makes it possible to determine the nonlinear dispersion relation, and the nonlinear effect on the cut-off wavenumber.
TL;DR: In this article, the phase I of [H3N(CH2)3NH3]CdI4 • 2H2O (1) crystallizes with isolated [CdBr4]2-tetrahedra; monoclinic, C2/c, Z = 8, a = 1702.6(3), b= 1459.8(5), b = 1280.3 (4), c = 709.5(3) pm, and ß= 120.32° at 299 K.
Abstract: Abstract The phase I of [H3N(CH2)3NH3]CdI4 • 2H2O (1) crystallizes with isolated [CdI4]2-tetrahedra; monoclinic, C2/c, Z = 8, a = 1702.6(3), b= 1459.3(3), c= 1555.5(3) pm, and ß= 120.32(3)° at 299 K. (1) shows a first-order phase transition at T1↔II = 245 K. The eight 127I(v1) NQR lines in phase II change discontinuously into four lines in phase I. The transition entropy from DSC measurements, ∆S = 5.0 J K1- mol-1 , shows that this transition is probably due to order-disorder of cations. [H3CNH2(CH2)3NH3]CdBr4 (2) crystallizes with isolated [CdBr4]2- tetrahedra; orthorhombic P212121, Z = 4,a= 1447.8(5), b = 1280.3 (4), c = 709.7(3) pm at 299 K. (2) shows four 81Br NQR lines between II and around 325 K, above which temperature the lines disappear. [(CH3)4N]2CdBr4 (3) shows a second-order phase transition at T1↔II = 271 K. Three of four 81Br NQR lines in phase II disappear below this transition point, the other line can be observed up to 315 K. The transition entropy, ∆S = 9.01 J KT-1 mol-1 , indicates that the transition is an order-disorder type of the cations. [(CH3)3S]2CdBr4 (4) shows a first-order type phase transition at T1↔II = 304 K. The four lines spectrum of 81Br NQR is observed in phase II and disappears above the transition point. The transition entropy, ∆S = 46.8 J K- 1 mol-1 is abnormally large. The role of the hydrogen bond and the bridging power between the halogen and cadmium atoms upon the formation of the condensed anion structure is discussed.
TL;DR: In this article, electric field gradients at Hg were determined in mercury mercaptides Hg(S(CH2)i CH3)2 experimentally for i ∈ {0, 1, 2} using time differential perturbed angular correlation and theoretically with the full potential linearized augmented plane wave code WIEN95.
Abstract: Abstract Electric field gradients (EFG) at Hg were determined in mercury mercaptides Hg(S(CH2)i CH3)2 experimentally for i ∈ {0, 1, 2} using time differential perturbed angular correlation and theoreti-cally for i ∈ {0, 1} with the full potential linearized augmented plane wave code WIEN95. Due to the large unit cells and small hydrogen atoms not full convergence of the plane wave basis set could be reached. Nevertheless, the calculated EFGs agree with experimental values to better than 20%. Furthermore, isolated molecules for i ∈ {0, 1) were investigated theoretically, and strong differences to the values for the crystalline state, especially for the asymmetry parameters η, were found.
TL;DR: Li3InBr6 and NaInBr4 have been synthesized and characterized by means of DTA, 81Br NQR, 6Li, 7Li, 23Na, and 115In NMR, and AC conductivity.
Abstract: Abstract Li3InBr6 and NaInBr4 have been synthesized and characterized by means of DTA, 81Br NQR, 6Li, 7Li, 23Na, and 115In NMR, and AC conductivity. These measurements revealed the presence of phase transitions and cationic diffusion in both compounds. From the spin-lattice relaxation times of 81Br NQR and the peak widths of 7Li and 23Na NMR spectra, it is deduced that the conduction is due to cationic diffusion. The activity energy for the Li+ diffusion was found to be 24 kJ/mol for Li3InBr6 .
TL;DR: In this article, the internal cation mobility ratios in the molten system KCl-DyCl3 have been measured at 1093 K by Klemm's countercurrent electromigration method.
Abstract: Abstract Internal cation mobility ratios in the molten system KCl-DyCl3 have been measured at 1093 K by Klemm's countercurrent electromigration method. From these, and data available on the conductivities and molar volumes of the mixtures, the internal mobilities b of both cations have been calculated. With increasing concentration of Dy, bK decreases. The decrease of bK is attributed to the tranquilization effect by Dy3+ ions which strongly interact with Cl- ions. With increasing concentration of K+ , bDy decreases; this may be attributed to the stronger association of Dy3+ with C- ions due to the enhanced charge asymmetry of the two cations neighboring to the C- ions. It could not been clarified whether a species such as [DyCl6]3- is also an electrically-conducting species in the K+ rich range.
TL;DR: In this paper, triple-zeta in the valence space plus polarisation functions (TZVP) for the equilibrium geometry stage is presented at a standardised level of calculation; all-electron MP2 correlation is included in all these studies.
Abstract: Abstract Ab initio determination of the electric field gradient (EFG) tensors at halogen and other centres ena-bled determination of the nuclear quadrupole coupling constants (NQCC) for a diverse set of C2v , C3v and other symmetry molecules of general formula MH2X2 and MHX3 , where the halogen atoms (X) are Cl, Br and I, and the heavy central atoms (M) are C and Si. The study presents results at a standardised level of calculation, triple-zeta in the valence space plus polarisation functions (TZVP) for the equilib-rium geometry stage; all-electron MP2 correlation is included in all these studies. For the bromo and iodo compounds, especially the latter, it is essential to allow core polarisation, by decontraction of the p,d-functions. This is conveniently done by initial optimization of the structure with a partly contract-ed basis, followed by reestablishment of the equilibrium structure with the decontracted basis. The NQCCs, derived from the EFGs, using the 'best' values for the atomic quadruple moments Cl, Br and I, lead to good agreement with the inertial axis (IA) data obtained from microwave spectroscopy. When the data from the present study is plotted against the values derived from the IA data, obtained by whatever approximations chosen by the MW authors, we obtain a linear regression for the data (85 points) with the slope 1.0365 and intercept -0.1737, with standard errors of 0.0042 and 0.2042, respectively; these are statistically identical results irrespective of whether the data is restricted to IA or EFG principal axis (PA) data. Since as in the C3v MH3X compounds studied previously, a close correlation of the microwave spectral data with the calculations was observed using the 'best' current values for Qz , there seems no need to postulate that the values of QBr for both 79Br and 81Br are seriously in error. A scaling downwards of Qz by about 5% for Br and I increases the agreement with experiment, but the contributions of relativistic effects are unknown, and could lead to further reassessment. Of the two common assumptions used in MW spectroscopy, to convert from IA to EFG-PA data, either (a) cylindrical symmetry of the NQCC along the bond direction, or (b) coincidence of the tensor principal element with the bond axis, the latter is found to be a much more realistic approximation.
TL;DR: In this paper, the rotational transition of the PH radical in its ground electronic (XΣ ) and vibrational states has been measured with the Cologne terahertz spectrometer in the frequency region between 920 and 1070 GHz.
Abstract: The N = 2 1 rotational transition of the PH radical in its ground electronic (XΣ ) and vibrational states has been measured with the Cologne terahertz spectrometer in the frequency region between 920 and 1070 GHz. The PH radical was generated by immersing red phosphorus in a dc glow discharge of molecular hydrogen buffered with argon. Transition frequencies of the five J0 J 00 fine structure components together with the associated hyperfine structure patterns were precisely measured and analyzed to derive highly accurate molecular parameters, which are more extensive than those reported in the existing literature. Among the determined parameters are the rotational constant B0 = 252200:8099(63) MHz and the centrifugal distortion constant D0 = 13:2915(33) MHz, as well as two fine structure constants – the spin-rotation constant 0 and the spin-spin interaction constant 0 – together with their centrifugal distortion contributions D 0 and D 0 . Furthermore, each of the magnetic hyperfine parameters bF, c, and the nuclear spin-rotation constants CI were obtained for both nuclei. The accuracy of previously obtained molecular constants has been improved by up to one order of magnitude. This new set of molecular parameters allows highly reliable frequency predictions of the rotational spectrum extending into the far infrared region; such transition frequencies may be of interest for interstellar spectroscopy.
TL;DR: In this article, 13C NMR spectroscopic measurements of aqueous solutions containing alkaline earth metal chloride and a carboxylic acid have been carried out to acquire some insight into the coordination manners of various carboxyllic acids to earth metal ions.
Abstract: Abstract 13C NMR spectroscopic measurements of aqueous solutions containing alkaline earth metal chloride and a carboxylic acid have been carried out to acquire some insight into the coordination manners of various carboxylic acids to alkaline earth metal ions. The dependence of the 13C NMR signal positions of the carboxylate carbons on the magnesium ion concentration in a magnesium carboxylate system is a good index to understand the coordination manner of the carboxylate ion. The upfield shift of the carboxylate carbon signal with increasing magnesium ion concentration indicates that the carboxylate ion acts as a bidentate ligand to form a ring structure. Only in the citrate systems, the existence of a relatively stable complex is evidenced in which the citrate ion is expected to act as a tridentate ligand.
TL;DR: In this paper, the authors presented ab initio calculations of EFGs at impurities in a TiO2 crystal using the KKR method within the muffin-tin approximation and based on the local density approximation.
Abstract: Abstract We present ab initio calculations of EFGs at impurities in a TiO2 crystal. They are directly calculated from the self consistent charge distribution which is determined by the KKR method within the muffin-tin approximation and based on the local density approximation. Impurities in the crystal are simulated by the super-cell method. Considering the charge state of Sc, Ti, Nb, Cd, Ta impurities in the TiO2 , the experimental values were well reproduced. The electronic structure of these impurities is discussed by analyzing the calculated density of states.
TL;DR: In this paper, the chemical shift (δ), linewidth (Δ), and line intensity (I) of the 63Cu NMR signal in these mixed solvents have been measured relative to the 63cu signal in 0.064 M copper(I) Perchlorate (CuClO4) solution in pure acetonitrile (AN) using a 500 MHz NMR Spectrometer and Ubbelohde viscometer.
Abstract: Abstract 63Cu nuclear magnetic resonance and viscosity studies of 0.064 M copper (I) Perchlorate solutions have been made at 298 K in binary mixtures of acetonitrile (AN) with dimethylsulphoxide (DMSO), hexamethylphosphotriamide (HMPA), N,N-dimethylacetamide (DMA), nitromethane (NM), propylene carbonate (PC) and 3-hydroxypropionitrile (3 HPN) at several compositions of the mixtures using a 500 MHz NMR Spectrometer and Ubbelohde viscometer, respectively. The chemical shift (δ), linewidth (Δ) and line intensity (I) of the 63Cu NMR signal in these mixed solvents have been measured relative to the 63Cu signal in 0.064 M copper (I) Perchlorate (CuClO4) solution in pure AN. The quadrupolar re-laxation rates (1/T2)Q, reorientational correlation times (τR) and quadrupolar coupling constants (QCC) of the copper (I) solvates have also been estimated from the data. The QCC values show a big variation in all solvent systems with the change of solvent composition, indicating the formation of mixed com-plexes. The variation of all NMR parameters with solvent composition shows strong effects of DMSO, HMPA, and DMA on the solvation behaviour of Cu + in the first three mixtures, and relatively much weaker effects of PC, NM and 3HPN in the other three mixtures.