Published by De Gruyter

Volume 54 Issue 10-11

Issue of Zeitschrift für Naturforschung A

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Open Access June 2, 2014

Pressure and Isotropic-Nematic Transition Temperature of Model Liquid Crystals

Siegfried Hess, Bin Su

Page range: 559-569

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Abstract

The pressure in the gaseous, the isotropic liquid and nematic liquid crystalline states, as well as the isotropic-nematic transition temperature are calculated for a model system composed of non-spherical particles. The potential is a generalization of the Lennard-Jones interaction where the attractive part depends on the relative orientations of the particles and the vector joining their centers of mass. Point of departure is an augmented van der Waals approach. It involves a modified Carnahan-Starling expression associated with the repulsive part of the interaction, and an orientation dependent second virial coefficient, as well as the orientational distribution functions of a pair of particles, linked with the attractive part of the potential. In a high temperature approximation, and for a special choice of model parameters, results are presented and displayed graphically.

Open Access June 2, 2014

Ionic Interactions in Alkali -Aluminium Tetrafluoride Clusters

Z. Akdeniz, Z. Çiçek, A. Karaman, G. Pastore, M. P. Tosi

Page range: 570-574

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Abstract

Complex anion structures ((AlF 4 ) - , (AlF 5 ) 2- and (AIF 6 ) 3- ) coexist in liquid mixtures of alu-minium trifluoride and alkali fluorides in composition-dependent relative concentrations and are known to interact with the alkali counterions. We present a comparative study of the static and vibrational structures of MA1F 4 molecules (with M = any alkali), with the aim of developing and testing a refined model of the ionic interactions for applications to the M-Al fluoride mixtures. We find that, whereas an edge-bridged coordination is strongly favoured for Li in LiAlF 4 , edge-bridging and face-bridging of the alkali ion become energetically equivalent as one moves from Na to the heavier alkalis. This result is sensitive to the inclusion of alkali polarizability and may be interpreted as implying (for M = K, Rb or Cs) almost free relative rotations of the M + and (AlF 4 ) - partners at temperatures of relevance to experiment. The consistency of such a viewpoint with electron diffraction data on vapours and with Raman spectra on melts is discussed.

Open Access June 2, 2014

A Theoretical Study of the Stabilization of the (AlF₅)^2— Complex Anion by Alkali Counterions

Z. Akdeniz, Z. Çiçek, A. Karaman, G. Pastore, M. P. Tosi

Page range: 575-578

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Abstract

We evaluate the relative stability of various states of coordination for the aluminium ion by fluorines in M n AlF n+3 microclusters, with M = Li, Na or K and n = 2 or 3. The calculations use ionic model interactions which have been adjusted and tested against experimental data and ab initio calculations on the (AlF 4 ) - anion and on MAlF 4 clusters. We confirm earlier results showing that the fivefold (AlF 5 ) 2- anion is stabilized by the counterions and assess the sensitivity of this result to the details of the model as well as the effect of alkali substitution. We evaluate the variation of the breathing mode frequency of the complex anions in these clusters for comparison with Raman scattering data from liquid mixtures ofAlF 3 and MF in the basic range of composition.

Open Access June 2, 2014

Stoichiometry Effects on the Electrical Conductivity of Lithium-Manganese Spinels

C. B. Azzoni, M. C. Mozzati, A. Paleari, M. Bini, D. Capsoni, V. Massarotti

Page range: 579-584

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Abstract

The electrical conductivity of lithium-manganese spinels is analyzed in samples with different starting Li cationic fraction x. Li-rich spinels, resulting from Li-Mn substitution around the stoi-chiometric value (x= 0.333), show conductivity values higher than that observed in stoichiometric LiMn 2 O 4 . Besides, a conductivity drop, associated with a structural phase transition at about 290 K in LiMn 2 O 4 , progressively disappears by decreasing x, while it is absent in Li-rich samples. Stoi-chiometry effects on the concentration of charge carriers and on the available sites for the hopping transport process are evaluated, as well as the effects due to coexisting insulating phases. The role of the Jahn-Teller effect on the conductivity behaviour of stoichiometric and Li-poor spinels is also considered.

Open Access June 2, 2014

Nonlinear Dielectric Relaxation in Solutions of 6CHBT in Nonpolar Medium

P. Kędziora, J. Jadżyn, L. Hellemans

Page range: 585-589

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Abstract

The frequency dependence of the nonlinear dielectric increment was studied for benzene solutions of the nematogenic molecule 4-(trans-4'-n-hexylcyclohexyl)isothiocyanatobenzene (C 6 H 13 CyHx-Ph-N = C = S, 6CHBT) at 25°C. The increment was induced by a quasi-static electric field of high strength (10 7 V/m), and its relaxation was detected by an alternating field of low strength (10 2 V/m) in the fre-quency range 1 MHz-3 GHz. The results are discussed in the framework of Coffey's theory.

Open Access June 2, 2014

DSC Investigations of the Phase Transitions of [M(NH₃ )₆](ClO₄)₂ and [M(NH₃)₆](BF₄)₂ , where M = Co and Cd

A. Migdał-Mikuli, E. Mikuli, S. Wróbel, Ł. Hetmańczyk

Page range: 590-594

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Abstract

Solid polymorphism of four compounds of the type [M(NH 3 ) 6 ](XY 4 ) 2 , where M = Co 2+ or Cd 2+ , and XY 4 = ClO 4 - or BF 4 - has been studied at 100 -300 K by DSC. One or two phase transitions of the investigated compounds have been found. For the compounds with M = Co the phase transitions have not yet been described in the literature. For the compounds with M = Cd the phase transition-temperature is in good agreement with the results obtained by NMR and EPR. Generally, for [M(NH 3 ) 6 ](BF 4 ) 2 compounds (M = Mg, Fe, Co, or Ni) the phase transition temperature T Cl is lower than that for the corresponding [M(NH 3 ) 6 ](ClO 4 ) 2 , but for compounds with M = Cd it is higher. However, the enthalpy and entropy changes at the T CI phase transitions of [M(NH 3 ) 6 ](BF 4 ) 2 are always lower than those for [M(NH 3 ) 6 ](ClO 4 ) 2 . Moreover, for the compounds of this type a correlation between the transition temperature T Cl and the crystal lattice parameter a has been found.

Open Access June 2, 2014

DSC Investigations of the Phase Transitions of [M(H₂O)₆](NO₃)₂ , where M = Mn, Co, Ni, Cu and Zn

E. Mikuli, A. Migdał-Mikuli, S. Wróbel, B. Grad

Page range: 595-598

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Abstract

The phase transitions of [M(H 2 O) 6 ](NO 3 ) 2 , where M = Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ or Zn 2+ have been studied at 100 -400 K by DSC. Two phase transitions connected with a two-stage melting process have been found for these five compounds. For the compound with M = Co, besides the two melting points a solid-solid phase transition at 272 K has been found.

Open Access June 2, 2014

Structure and Thermodynamic Properties of Molten Rare Earth-Alkali Chloride Mixtures

Yoshihiro Okamoto, Torn Ogawa

Page range: 599-604

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Abstract

The dependence of the enthalpy of mixing on the structure of molten rare earth-alkali chloride mixtures has been investigated by molecular dynamics simulation. The experimental enthalpy of the mixing with its negative and its dependence on the cation size was qualitatively reproduced. It became clear that the enthalpy of mixing depends on the structural features of short and medium range.

Open Access June 2, 2014

Al³⁺ Coordination in Cryolitic Melts: A Computer Simulation Study

Michael J. Castiglione, Mauro C. C. Ribeiro, Mark Wilson, Paul A. Madden

Page range: 605-610

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Abstract

The structures of melts containing cryolite have proved difficult to confirm, despite decades of study, on account of the high temperatures and corrosiveness of these melts. Raman spectroscopy has so far provided the majority of the insight into the aluminium coordination environments, but some of its interpretations are still debated. In this paper we present the results of MD simulations on various NaF-AlF 3 liquid mixtures using published potentials developed for the solid state and published Raman spectra.

Open Access June 2, 2014

Estimation of Lattice Energies of Organic Molecular Crystals by Combination of Experimentally Determined and Quantum- Chemically Calculated Quantities: A New Value for the Lattice Energy of a-Glycine

Gerhard Raabe

Page range: 611-616

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Abstract

A new value for the lattice energy of a-glycine was determined by combination of the experimentally measured heat of sublimation taken from literature and the quantum-chemically calculated energy difference E tot , gp - E tot,cry , where E tot,gp is the total energy of the most stable form of the compound in the gas phase (carboxylic acid) and E tot,cry the total energy of the molecule as it occurs in its crystalline form (betaine). At the highest levels of ab initio theory employed in this study this energy difference is -(28±2) kcal/mol, indicating that older work overestimated this difference significantly. The reason for the overestimation of this energy difference was determined by means of additional ab initio calculations. The lattice energy of -(67±2)kcal/mol obtained using the new value for E tot,gp - E tot,cry is significantly more positive than an older value of -103 kcal/mol frequently cited in the literature.

Open Access June 2, 2014

Collective Bursting in Populations of Intrinsically Nonbursting Neurons

Daniel A. Blank, Ruedi Stoop

Page range: 617-627

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Abstract

We describe a novel type of bursting that we observe in simulations of large recurrent networks of biophysically plausible, intrinsically non-bursting neurons. The mechanism responsible for the bursting is a combination of excitatory feedback received from neighbouring neurons, together with an activity-dependent adaptation mechanism that slows down spiking. During the bursting phases, the firing patterns are not repeated and the lengths of the interburst intervals are varying. We develop a simple phenomenological model that captures most qualitative aspects of the observed collective bursting. We compare the parameter range leading to bursting in the phenomenological model, with parameter estimates from cortical anatomy and physiology, and conjecture that the discovered new type of bursting should also be observable in biological neocortical networks.

Open Access June 2, 2014

Isolated versus Condensed Anion Structure V: X-ray Structure Analysis and ⁸¹Br NQR of t-butylammonium tribromocadmate(II)-1/2 water, i-propylammonium tribromocadmate(II), and tris-trimethylammonium heptabromodicadmate(II)

Hideta Ishihara, Keizo Horiuchi, Shi-qi Dou, Thorsten M. Gesing, J.-Christian Buhl, Helmut Paulus, Ingrid Svoboda, Hartmut Fuess

Page range: 628-636

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Abstract

The crystal structures of the condensed bromocadmate anions with chains built of [CdBr 3 ] ∞ were de-termined by X-ray structure analysis at 300 K. In addition, the temperature dependence of the 81 Br NQR frequencies was observed. [(t-C 4 H 9 NH 3 )CdBr 3 ] 2 -H 2 O (1) tallizes with a double Br bridged chain (monoclinic, P2/c, Z = 4, a = 1963.4(8), b 87.7(4), c 1432.1(6) pm, and ß= 110.66(2)°). Six 81 Br NQR lines are observed at temperatures between 77 and 330 K. (i-C 3 H 7 NH- 3 )CdBr 3 (2) crystalliz-es with a triple Br bridged chain (orthrhombic, Pbca, Z= 8, a = 1975.4(6), b = 1415.8(4), c = 690.1(2) pm). (2) shows three 81 Br NQR lines at temperatures between 77 and 193 K. A phase transition occurs at 224 K. The structure of [(CH 3 ) 3 NH] 3 Cd 2 Br 7 ] (3) was redetermined. (3) consists of a triple Br bridged chain and a discrete [CdBr 4 ] tetrahedron (hexagonal, P6 3 mc, Z= 8, a = 1483.5(2), c = 685.7(5) pm). The structure of (3) is identical to the one reported by Daoud, Perret, and Dusausoy, Acta Crystallogr., B35, 2718 (1979). Three 81 Br NQR lines are observed at temperatures between 77 and 243 K.

Open Access June 2, 2014

On the Relativistic Invariance of Maxwell's Equation

Oleg D. Jefimenko

Page range: 637-644

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Abstract

It is common knowledge that Maxwell's electromagnetic equations are invariant under relativistic transformations. However the relativistic invariance of Maxwell's equations has certain heretofore over-looked peculiarities. These peculiarities point out to the need of reexamining the physical significance of some basic electromagnetic formulas and equations.

Open Access June 2, 2014

Third-order Optical Nonlinearities of Higher Fullerene and Carbon Nanotube

Rui-Hua Xie, Qin Rao

Page range: 645-658

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Abstract

Recent theoretical and experimental studies on the third-order optical nonlinearities of higher fullerenes including C 70 , C 76 , C 84 , C 86 , C 90 , C 94 and C 96 are briefly reviewed. The extended Su-Schrieffer-Heeger model is introduced and applied to study the third-order optical nonlinearity of chiral carbon nanotubes (CCN), where the average contribution Γ of one carbon atom to the third-order optical nonlinearity of each CCN is calculated and compared with that of a well characterized polyenic polymer. It is found that (i) the smaller the diameter of a CCN, the larger the average contribution Γ; (ii) the metallic CCN favors larger third-order optical nonlinearity than the semiconducting one; (iii) CCN can compete with the conducting polymer achieving a large third-order optical susceptibility. Also the doping effect on the second-order hyperpolarizability of a tubular fullerene is investigated. It is found that the doping effect increases greatly the magnitude of the second-order hyperpolarizability of tubular fullerene.

Open Access June 2, 2014

Mean Amplitudes of Vibration of the Novel SbF₇^2-, BiF₇^2- and Dianions

E. J. Baran

Page range: 659-660

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Abstract

Mean amplitudes of vibration of the recently reported pentagonal bipyramidal SbF 7 2- and BiF 7 2- dianions were calculated from vibrational spectroscopic data, in the temperature range between 0 and 1000 K. The results are briefly discussed and some comparisons with related species are made.

Open Access June 2, 2014

Dielectric Relaxation of Hexadeutero Dimethylsulfoxide

H. Betting, M. Stockhausen

Page range: 661-661

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Abstract

The dielectric relaxation parameters of the title substance (DMSO-d 6 ) in its pure liquid state are determined from meas-urements up to 72 GHz at 20°C in comparison to protonated DMSO. While the relaxation strengths do not differ, the relax-ation time of DMSO-d 6 is significantly longer (21.3 ps) than that of DMSO (19.5 ps).

Open Access June 2, 2014

Errata

Page range: 662-662

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Abstract

The stated authorship of this paper (Rui-Hua Xie and Paul Brumer) is incorrect. Spe-cifically, work on this topic was proposed by Professor Aephraim Steinberg (Univer-sity of Toronto) and carried in collaboration with Professors Steinberg and Paul Bru-mer, and with Navin Bhat (University of Toronto). Decisions about the suitability of the research for publication, and the writing and submission of the manuscript for publication, were actions taken by Rui-Hua Xie without the knowledge or approval of Brumer or his coworkers. As such, Rui-Hua Xie is the sole author of this paper and bears full responsibility for its contents.

About this journal

Objective
A Journal of Physical Sciences: Zeitschrift für Naturforschung A (ZNA) is an international scientific journal which publishes original research papers from all areas of experimental and theoretical physics. Authors are encouraged to pay particular attention to a clear exposition of their respective subject, addressing a wide readership. In accordance with the name of our journal, which means “Journal for Natural Sciences”, manuscripts submitted to ZNA should have a tangible connection to actual physical phenomena. In particular, we welcome experiment-oriented contributions.

Manuscripts considered for publication in A Journal of Physical Sciences: Zeitschrift für Naturforschung A undergo high-level refereeing. Mere formal correctness of a paper is not sufficient for its acceptance. Moreover, articles reporting a merely marginal extension of already existing knowledge are considered unsatisfactory. Instead, the key quality a publication in A Journal of Physical Sciences: Zeitschrift für Naturforschung A should possess is that it makes a genuine contribution to the advancement of its topic.

Topics

Atomic, Molecular & Optical Physics
Chemical Physics
Dynamical Systems & Nonlinear Phenomena
Fundamental Concepts of Physical Sciences
Gravitation & Cosmology
Hydrodynamics & Plasma Physics
Nuclear Physics & Particle Physics
Quantum Field Theory
Solid State Physics & Materials Science
Thermodynamics & Statistical Physics
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Original research articles, research notes, letters and review articles from all areas of theoretical and experimental physics

Information on submission process

Volume 54 Issue 10-11

Issue of Zeitschrift für Naturforschung A

Pressure and Isotropic-Nematic Transition Temperature of Model Liquid Crystals

Abstract

Ionic Interactions in Alkali -Aluminium Tetrafluoride Clusters

Abstract

A Theoretical Study of the Stabilization of the (AlF5)2— Complex Anion by Alkali Counterions

Abstract

Stoichiometry Effects on the Electrical Conductivity of Lithium-Manganese Spinels

Abstract

Nonlinear Dielectric Relaxation in Solutions of 6CHBT in Nonpolar Medium

Abstract

DSC Investigations of the Phase Transitions of [M(NH3 )6](ClO4)2 and [M(NH3)6](BF4)2 , where M = Co and Cd

Abstract

DSC Investigations of the Phase Transitions of [M(H2O)6](NO3)2 , where M = Mn, Co, Ni, Cu and Zn

Abstract

Structure and Thermodynamic Properties of Molten Rare Earth-Alkali Chloride Mixtures

Abstract

Al3+ Coordination in Cryolitic Melts: A Computer Simulation Study

Abstract

Estimation of Lattice Energies of Organic Molecular Crystals by Combination of Experimentally Determined and Quantum- Chemically Calculated Quantities: A New Value for the Lattice Energy of a-Glycine

Abstract

Collective Bursting in Populations of Intrinsically Nonbursting Neurons

Abstract

Isolated versus Condensed Anion Structure V: X-ray Structure Analysis and 81Br NQR of t-butylammonium tribromocadmate(II)-1/2 water, i-propylammonium tribromocadmate(II), and tris-trimethylammonium heptabromodicadmate(II)

Abstract

On the Relativistic Invariance of Maxwell's Equation

Abstract

Third-order Optical Nonlinearities of Higher Fullerene and Carbon Nanotube

Abstract

Mean Amplitudes of Vibration of the Novel SbF72-, BiF72- and Dianions

Abstract

Dielectric Relaxation of Hexadeutero Dimethylsulfoxide

Abstract

Errata

Abstract

A Theoretical Study of the Stabilization of the (AlF₅)^2— Complex Anion by Alkali Counterions

DSC Investigations of the Phase Transitions of [M(NH₃ )₆](ClO₄)₂ and [M(NH₃)₆](BF₄)₂ , where M = Co and Cd

DSC Investigations of the Phase Transitions of [M(H₂O)₆](NO₃)₂ , where M = Mn, Co, Ni, Cu and Zn

Al³⁺ Coordination in Cryolitic Melts: A Computer Simulation Study

Isolated versus Condensed Anion Structure V: X-ray Structure Analysis and ⁸¹Br NQR of t-butylammonium tribromocadmate(II)-1/2 water, i-propylammonium tribromocadmate(II), and tris-trimethylammonium heptabromodicadmate(II)

Mean Amplitudes of Vibration of the Novel SbF₇^2-, BiF₇^2- and Dianions