共查询到7条相似文献,搜索用时 0 毫秒
1.
ZHU Lin YAO Kai-Lun LIU Zu-Li 《理论物理通讯》2007,48(5):921-924
Ab initio within the full potential linearized augmented plane wave (FP-LAPW) method with the GGA+U approach is applied to study the electronic structures of two compounds NaK3(NpO2)4(SO4)4(H2O)2 and NaNpO2SO4H2O. The present calculations show that the major part of the spin magnetic moment in these two compounds is from Np(V) ions, and the origin of the cation-cation interactions between Np comes from the spin polarization effect within Np-ONv-Np bonds. 相似文献
2.
Peter Klaeboe Claus J. Nielsen Anne Horn Gamil A. Guirgis Kathleen V. Kilway 《Journal of Raman spectroscopy : JRS》2009,40(12):2111-2122
Infrared spectra of 1,2‐bis(trifluorosilyl)ethane (SiF3CH2CH2SiF3) were obtained in the vapour and liquid phases, in argon matrices and in the solid phase. Raman spectra of the compound as a liquid were recorded at various temperatures between 293 and 270 K and spectra of an apparently crystalline solid were observed. The spectra revealed the existence of two conformers (anti and gauche) in the vapour, liquid and in the matrix. When the vapour was chock‐frozen on a cold finger at 78 K and annealed to 150 K, certain weak Raman bands vanished in the crystal. The vibrational spectra of the crystal demonstrated mutual exclusion between IR and Raman bands in accordance with C2h symmetry. Intensity variations between 293 and 270 K of pairs of various Raman bands gave ΔH(gauche—anti) = 5.6 ± 0.5 kJ mol−1 in the liquid, suggesting 85% anti and 15% gauche in equilibrium at room temperature. Annealing experiments indicate that the anti conformer also has a lower energy in the argon matrices, is the low‐energy conformer in the liquid and is also present in the crystal. The spectra of both conformers have been interpreted, and 34 anti and 17 gauche bands were tentatively identified. Ab initio and density functional theory (DFT) calculations were performed giving optimized geometries, infrared and Raman intensities and anharmonic vibrational frequencies for both conformers. The conformational energy difference derived in CBS‐QB3 and in G3 calculations was 5 kJ mol−1. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
3.
María E. Defonsi Lestard María E. Tuttolomondo Eduardo L. Varetti Derek A. Wann Heather E. Robertson David W. H. Rankin Aida Ben Altabef 《Journal of Raman spectroscopy : JRS》2009,40(12):2053-2062
The molecular structure of methyl trifluoroacetate (CF3C(O)OCH3) has been determined in the gas phase from electron‐diffraction data supplemented by ab initio (MP2) and DFT calculations using different basis sets. Experimental data revealed an anti conformation with a dihedral angle θ (CCOC) = 180°. Quantum mechanical calculations indicate the possible existence of two conformers, differing by a rotation about the C(O) O bond. The global minimum represents a Cs‐symmetric structure in which the CF3 group has the anti orientation with respect to the CH3 group, but there is another potential minimum, much higher in energy, representing a Cs‐symmetric structure with a cis conformation. The preference for the anti conformation was studied using the total energy scheme and the natural bond orbital (NBO) partition scheme. Additionally, the total potential energy has been deconvoluted using a six‐fold decomposition in terms of a Fourier‐type expansion, showing that the electrostatic and steric contributions are dominant in stabilizing the anti conformer. Infrared spectra of CF3C(O)OCH3 were obtained for the gaseous and liquid phases, while the Raman spectrum was recorded for the liquid phase. Harmonic vibrational frequencies and a scaled force field have been calculated, leading to a final root mean‐square deviation of 9 cm−1 when comparing experimental and calculated frequencies. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
4.
In a simple hadronic model, the two-photon exchange contributions tothe single spin asymmetries for the nucleon and the 3He are estimated. The results show that the elastic contributions of two-photon exchange to the single spin asymmetries for the nucleon are rather small while those for the 3He are relativelylarge. Besides the strong angular dependence, the two-photon contributions to the single spin asymmetry for the 3He are very sensitive to the momentum transfer. 相似文献
5.
采用传统的高温固相烧结法制备了双层钙钛矿锰氧化物(La1-xGdx)4/3Sr5/3Mn2 O7 (x=0, 0.025)多晶样品. 通过X射线衍射仪研究发现样品为Sr3Ti2O7型四方结构, 空间群为I4/mmm; 磁性测量表明, Gd3+掺杂后的样品(La0.975Gd0.025)4/3Sr5/3Mn2O7的三维磁有序转变温度(TC13D)、磁化强度(M)均降低, 这是由于Gd3+的掺杂引起晶格的畸变, 从而使得晶格常数发生改变, 减弱了铁磁耦合而导致的; 通过电子自旋共振谱测量发现, 在TC3D<T<300 K温度范围内, 两样品在顺磁的基体上均有短程的铁磁团簇存在, 出现了相分离现象. 电性测量表明: 两样品分别在TC13D (La4/3Sr5/3Mn2O7 样品的三维磁有序转变温度, TC03D)<T<300 K温度范围内均以三维变程跳跃的方式导电, 分析得出Gd3+的掺杂使得载流子局域长度的减小. 这表明载流子需要吸收更多的能量才能克服晶格的束缚进行跳跃, 因此(La0.975Gd0.025)4/3Sr5/3Mn2 O7 样品的电阻较高. 相似文献
6.
S. Sidi Ahmed G. Dimitri Ngantso M. Boujnah A. Benyoussef A. El Kenz 《Physics letters. A》2019,383(2-3):121-126
By using the density functional theory (DFT) and Monte Carlo simulations (MCS) with the Heisenberg model, we have studied magnetic properties of the bulk perovskite YCrO3. The exchange couplings of the Heisenberg model and the magnetic anisotropy are investigated. The 110 direction in the crystalline structure of the compound has shown the minimum energy, it is the easy magnetic direction. Using Monte Carlo simulations, the magnetizations behavior, the effects of system parameters and the critical exponents of the compound YCrO3 are implemented. It is shown that the bulk perovskite YCrO3 belongs to the 3D Heisenberg universality class. 相似文献
7.
G. Roux S. Capponi P. Lecheminant P. Azaria 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):293-308
We study spin 3/2 fermionic cold atoms with attractive interactions confined in a one-dimensional optical lattice. Using numerical
techniques, we determine the phase diagram for a generic density. For the chosen parameters, one-particle excitations are
gapped and the phase diagram is separated into two regions: one where the two-particle excitation gap is zero, and one where
it is finite. In the first region, the two-body pairing fluctuations (BCS) compete with the density ones. In the other one,
a molecular superfluid (MS) phase, in which bound-states of four particles form, competes with the density fluctuations. The
properties of the transition line between these two regions is studied through the behavior of the entanglement entropy. The
physical features of the various phases, comprising leading correlations, Friedel oscillations, and excitation spectra, are
presented. To make the connection with experiments, the effect of a harmonic trap is taken into account. In particular, we
emphasize the conditions under which the appealing MS phase can be realized, and how the phases could be probed by using the
density profiles and the associated structure factor. Lastly, the consequences on the flux quantization of the different nature
of the pairing in the BCS and MS phases are studied in a situation where the condensate is in a ring geometry. 相似文献