Dynamical and static spin conductivities in the Heisenberg model on honeycomb lattice: The effects of magnetic long range ordering

We have studied both dynamical and static spin conductivities of Heisenberg antiferromagnet on honeycomb lattice in the presence of a magnetic long range ordering. The effects of spatial anisotropy as weak Dzyaloshinskii–Moriya interaction and next nearest neighbor exchange coupling on the behaviors of conductivities are discussed. A sublattice antiferromagnetic long range ordering has been considered for localized electrons on honeycomb lattice structure. Using Holstein–Primakoff bosonic transformations, the behaviors of spin transport properties have been studied by means of excitation spectrum of mapped bosonic gas. We have found the temperature dependence of static spin conductivity in the field induced gapped spin-polarized phase for various Dzyaloshinskii–Moriya interaction strengths. Furthermore we have studied the frequency dependence of dynamical spin conductivity for various Dzyaloshinskii–Moriya interaction strengths and different next nearest neighbor coupling constants. We find that the height of peak in the temperature dependence of static spin conductivity increases upon increasing the anisotropy parameter. The static spin conductivity is found to be monotonically increasing with anisotropy parameter due to increase of the energy gap in the excitation spectrum. Furthermore we have studied the temperature dependence of the spin conductivity for different next nearest neighbor coupling constants.     

The inversional dependence of hyperfine quadrupole coupling in 14NH3

A simple theoretical model explaining the inversional dependence of hyperfine quadrupole coupling in ¹⁴NH₃ is presented. The model, when related to available experimental hyperfine splittings, can be used to predict the effective hyperfine quadrupole coupling constants for all (low-lying) ro-inversional levels. The actual predictions reveal that the inversional dependence of the coupling constants is not only rather strong but also non-monotonic.     

Study of the Binding Energy of Relativistic Nuclear Matter in the Relativistic σ-ω-π Model

A relativistic σ-ω-π model is proposed to calculate the binding energy of relativistic nuclear matter. We put emphasis on the relativistic particle-hole, delta-hole excitation of pion propagator in nuclear matter. The renormalization of the nucleon self-energy in nuclear matter is made for the pseudo-vector πNN and πNΔ couplings by introducing corresponding form factor and by dispersion relation. We find that the density dependence correction to meson-NN coupling constants is very important to saturate the binding energy of nuclear matter. The density dependence correction to πNN and πNΔ coupling constants has the effect of softening the EOS of nuclear matter.     

The electric hyperfine interaction in group VI-a hexafluorides

The electric hyperfine interaction in group VI-a hexafluorides SF₆, SeF₆ and TeF₆ has been studied in the temperature range from 10 K to about 110K by means of the TDPAD method. The temperature dependence can be explained by Bayer — Kushida theory. The coupling constants decrease with increasing temperature. The strength of the temperature dependence diminishes from SF₆ to TeF₆, indicating an increase of ionicity of the bonds. If the coupling constants are plotted versus the elements of the fluorine compounds, characteristic trends can be seen. Therefore we predict the coupling constant of OF₂ to be about 100 MHzThis work was supported by the Bundesministerium für Forshung und Technologie     

Thermodynamic properties of Heisenberg model for magnetic ordered graphene sheet

We study the thermodynamic properties of two dimensional Heisenberg antiferromagnet on the honeycomb lattice in the presence of anisotropic Dzyaloshinskii-Moriya interaction and next nearest neighbor coupling exchange constant. A sublattice antiferromagnetic long range ordering has been considered for localized electrons on honeycomb lattice structure. In particular, the temperature dependence of specific heat has been investigated for various physical parameters in the model Hamiltonian. Using Holstein-Primakoff bosonic transformations, the behavior of thermodynamic properties has been studied by means of excitation spectrum of mapped bosonic gas. Furthermore we have studied the dependence of specific heat and magnetization on Dzyaloshinskii-Moriya interaction strength for various next nearest neighbor interaction strengths. At low temperatures, the specific heat is found to be monotonically increasing with temperature. We have found the dependence of specific heat on Dzyaloshinskii-Moriya interaction strength shows a monotonic increasing behavior for various next nearest neighbor exchange constants. Also we have studied the temperature dependence of staggered magnetization for different next nearest neighbor coupling constants. Our results show the critical temperature moves to higher amounts with reduction of Dzyaloshinskii-Moriya interaction strength.     

Magneto-elastic properties of Tb<Subscript>3</Subscript>Ga<Subscript>5</Subscript>O<Subscript>12</Subscript> (TGG)

The temperature dependence of the elastic constants in Tb₃Ga₅O₁₂ was measured and analysed with a simple crystal field model. The magneto-elastic coupling constants have been deduced from this experiment. The coupling constant g_Γ5, related to the c₄₄ mode, is anomalously large. These coupling constants are important for the interpretation of the phonon Hall effect.     

The Millimeter-Wave Spectrum of 2,3-Dihydrofuran

The millimeter-wave spectrum of 2,3-dihydrofuran in the ground and five ring-puckering excited states has been measured in the frequency range 100–250 GHz. The ground and first ring-puckering excited states have been fitted to a two-state Hamiltonian including Coriolis coupling interaction. The determined energy difference of 18.684(7) cm⁻¹between these states and theaandbtype coupling parameters are consistent with the ring-puckering potential function and the previously observed dependence of the centrifugal distortion constants Δ_JK, Δ_K, and δ_K. A small ring-puckering dependence of the quartic centrifugal distortion constants Δ_Jand δ_Jhas been also observed. This dependence is well accounted for in terms of the ring-puckering potential function and the vibrational dependence of the rotational constants.     

The conformational dependence of vicinal 15N-C-C-H coupling constants in peptides

The conformational dependence of vicinal ¹⁵N-C-C-H coupling in N-methylacetamide as a model compound for coupling in the peptide backbone is investigated by means of the self-consistent perturbation formulation for coupling constants in the INDO approximation of self-consistent-field molecular orbital theory. Because the calculated coupling constants cover a range of at least 7 Hz, they should be useful in determining the ψ angles in peptides. The prediction of opposite signs for gauche and trans coupling indicates the need for sign determination. Non-negligible coupling constants of positive sign for the gauche arrangements are undoubtedly due to a substituent effect involving the lone pair electrons on the nitrogen and the π-electrons of the carbonyl group. Calculated results are compared with the available experimental data.     

Analytical polarization and coherence transfer functions for three dipolar coupled spins 12

Analytical polarization and coherence transfer functions are presented for a spin system consisting of three dipolar coupled homonuclear spins 12 under energy matched conditions. Based on these transfer functions, optimal durations of Hartmann-Hahn mixing periods can be determined for arbitrary dipolar coupling constants D(12), D(13), and D(23). In addition, the dependence of the transfer efficiency on the relative size of the dipolar coupling constants is illustrated.     

丝氨酸及其La~(3+)配合物的~1H核磁共振谱参数的pH依赖性

本文测得不同pH值下丝氨酸及其La~(3+)配合物的~1H谱,用PANIC程序对谱图进行模拟,获得化学位移和偶合常数,考察了~1H核磁共振谱参数的pH依赖性,从理论上进行了解释,并由得到的偶合常数计算出丝氨酸及其La~(3+)配合物的三种构象的比例,讨论了它们在不同pH条件下的变化,这些结果为下一步的生物大分子的研究提供了有用的信息。     

Sensitivity of pion production to the nuclear EOS and to the delta's coupling constant

A relativistic baryon-meson mean field theory (including delta resonances) is used to study the dependence of pion production in heavy ion collisions on the nuclear equation of state and on the delta-meson coupling constants. For fixed ground state equations of state, the pion yields depend sensitively on the value of the delta-meson coupling constants.     

Analysis of the interactions in FCCF:(H2O) and FCCF:(H2O)2 complexes through the study of their indirect spin–spin coupling constants

A theoretical study of FCCF:(H₂O)_n complexes, with n?=?1 and 2, has been carried out by means of ab initio computational methods. Three kinds of interactions are observed in the complexes: H···π and H···F hydrogen bonds and O···FC tetrel bonds. The indirect spin–spin coupling constants have been calculated at the CCSD/aug-cc-pVTZ-J computational level. Special attention has been paid to the dependence of the different intramolecular coupling constants in FCCF on the distance between the coupled nuclei and the presence or absence of water molecules. The exceptional sensitivity shown by these coupling constants to the presence of water molecules is quite notorious and can provide information on the bonding structure of the molecule.     

核自旋偶合常数的计算(Ⅱ)简单分子(离子)偶合常数2J的计算

本文把计算隔一个化学键的偶合常数¹J的原理和方法推广到简单分子(离子)中隔两个化学键的偶合常数²J的计算。对10种氢化物和14种氟化物的计算结果表明,除了个别化合物的计算值与实验值相差较大外,一般都能较好地符合。     

Physical states and properties of barium titanate films in a plane electric field

The influence of a plane electric field on the phase states of barium titanate thin films under the conditions of forced deformation has been studied. The field dependence of a complete set of material constants has been taken in the region of the c-phase, where polarization losses are absent. The material constants are calculated using equations of the piezoelectric effect derived by linearizing the nonlinear equations of state from the phenomenological; theory for barium titanate. It has been shown that there is a critical value of the field at which the electromechanical coupling coefficient reaches a maximum.     

Influence of supercurrents on the stability of superconducting magnets

Supercurrents were recently identified as a source of reduced magnet stability which can explain the measured ramp rate limitation in large superconducting magnets. They also explain an unexpected periodic field modulation along the axes of superconducting accelerator dipoles. Supercurrents are extra coupling currents between the strands of a cable which are induced by a variable field sweep rate (x) along the length of the cable. They flow over the whole cable length and have time constants many orders of magnitudes larger than ‘normal' interstrand coupling currents. Supercurrents may lead to a highly inhomogeneous current distribution and to additional coupling losses (‘supercurrent losses'), even in magnet sections with =0. Both effects can drastically reduce the magnet stability during fast ramping up. The complete solution of the space and time dependence is given for a two-strand model cable. The theory of supercurrents can explain typical results of ramp rate limitation in large magnets.     

Spin dynamics near the Lifshitz point

Spin dynamics in the vicinity of Lifshitz points associated with Heisenberg and planar ferromagnets and antiferromagnets is discussed. Mode coupling arguments are used to obtain the dynamic exponents and the temperature dependence of the diffusion constants.     

Frequency-selective coupling in parallel dielectric waveguides

A formula for the efficiency of coupling of electromagnetic energy between dielectric waveguides which, in the absence of coupling, have unequal guided-mode propagation constants, is derived. This result is used in calculating the frequency dependence of coupling between non-identical slab waveguides.     

Universal features of terahertz absorption in disordered materials

Using an analytical theory, experimental terahertz time-domain spectroscopy data, and numerical evidence, we demonstrate that the frequency dependence of the absorption coupling coefficient between far-infrared photons and atomic vibrations in disordered materials has the universal functional form, C(omega)=A+Bomega(2), where the material-specific constants A and B are related to the distributions of fluctuating charges obeying global and local charge neutrality, respectively.     

Spin–spin coupling constants in linear substituted HCN clusters

The indirect nuclear spin–spin coupling constants of homogeneous hydrogen-bonded HCN clusters are compared with those of inhomogeneous HCN clusters where one of the terminal HCN molecules is substituted by its isomer HNC and by LiCN. Both the intra- and intermolecular (across the hydrogen bond) coupling constants are calculated for the linear form of the clusters containing up to three molecular monomers using different hybrid DFT functionals. The geometry of the monomers and clusters is optimised at the B3LYP/6-311++G(d,p) level. The effect of substitution by the ionic compound LiCN on the coupling constants of HCN is found to be more pronounced than that by HNC. The Ramsey parameters that form the total spin–spin coupling constants are also analysed individually. Among the four Ramsey parameters, the Fermi Contact term is found to be the dominant contributor to the total coupling constants in most cases. The presence of LiCN in the cluster tends to decrease the intramolecular Fermi Contact values, while HNC increases the same in all dimers and trimers. The contributions of localised molecular orbitals have been analysed for the HCN–HNC cluster to obtain some additional insight about the SSCC transmission mechanism along the coupling pathway.     

The application of maximum entropy processing to the deconvolution of coupling patterns in NMR

The deconvolution of J-coupling patterns in NMR by iterative maximum entropy processing is demonstrated. Both the in-phase and the antiphase coupling patterns are considered. The deconvolution of the coupling pattern, either for one value of the coupling constant (1D J deconvolution) or for a range of coupling constants (2D J deconvolution) is shown. It is demonstrated that the method can be used for improving the signal-to-noise ratio for known coupling patterns by removing the coupling structure, as well as for extracting coupling constants from an unknown spectrum. Examples are shown both in 1D NMR and in slicewise processing of 2D spectra.