共查询到20条相似文献,搜索用时 15 毫秒
1.
基于第一性原理的计算方法研究了纯CeO_2、Co掺杂CeO_2和同时引入氧空位Vo和Co掺杂的CeO_2稀磁半导体体系.通过计算体系的能带结构和态密度,探讨了该体系磁性产生的机制.计算发现,纯CeO_2体系不具有磁性;没有氧空位Vo的Co掺杂CeO_2体系中,Co离子之间通过O原子发生超交换反铁磁耦合,体系无铁磁性;当氧空位Vo和Co离子同时存在于CeO_2体系中时,Co离子之间通过氧空位Vo发生铁磁耦合,该体系表现出铁磁性能.另外,由氧空位Vo诱导的Co离子之间的铁磁耦合不仅发生在紧邻的两个Co离子,而且可以扩展到几个原子距离的长度.计算结果证明了氧空位Vo诱导铁磁性耦合机制.本文工作将为CeO_2基稀磁半导体体系制备与磁学性质的研究提供支持. 相似文献
2.
Evgenii E. Nikitin Alexandre I. Reznikov Stanislav Ya. Umanskii 《Molecular physics》2013,111(6):1301-1312
Processes of charge exchange of Ar+ +(3p 5) and Kr+ +(4p 5) on He(1s 2) at low collision energies are investigated theoretically. Semiempirical asymptotic calculations of the radial coupling between initial and final states (both neglecting and allowing for the spin-orbit interaction) are presented. The result of semiempirical calculation of the coupling is in reasonable agreement with an earlier ab initio calculation for the system ArHe+ +. The integral cross sections were estimated using the Landau-Zener model. Comparisons are made with available experimental data and numerical quantum calculation. 相似文献
3.
The spin-orbit coupling constants of BH+ and CH have been calculated using ab initio molecular SCF wavefunctions with the gaussian lobe function basis set. It is demonstrated that fair agreement with experimental values can be achieved even with a relatively small basis set, provided that no terms are neglected in calculating the matrix elements. 相似文献
4.
A simplified resonating-group method, called model K, is used to analyze 3He + nucleus scattering data for target nuclei with nucleon number ranging from 40 to 208 and for 3He energies ranging from 70 to 130 MeV. The results show that a rather satisfactory agreement between calculated and experimental
differential-scattering cross sections can be obtained if one allows the value of the exchange-mixture parameter in the nucleon-nucleon
potential to deviate somewhat from that in the corresponding N + nucleus case. With the model-K nonlocal interaction, an equivalent local internuclear potential is also constructed with
a WKB procedure. Here it is found that, with a proper consideration of nucleon-exchange effects, one can explain nearly all
of the energy dependence of the real part of the phenomenologically determined optical potential in 3He + nucleus scattering.
Received May 31, 1999; revised November 9, 1999; accepted for publication December 20, 1999 相似文献
5.
The electronic structure and magnetic properties of nonmagnetic phosphorus doped ZnO are investigated using first-principles calculation. Both generalized gradient approximation (GGA) and GGA + U calculations show that each substitutional P atom in ZnO induces a magnetic moment of about 1.0 μB, which come mainly from the partially filled p orbitals of the substitutional P and its 12 second neighboring O atoms. The magnetic coupling between the moments induced by P doping is ferromagnetic. The calculated electronic structures indicate that the ferromagnetic coupling can be explained in terms of the two band coupling model. 相似文献
6.
E. Kelm S. Korovin V. Pustovoy A. Surkov A. Vladimirov 《Applied physics. B, Lasers and optics》2011,105(3):599-606
Silicon nanoparticles (nSi) with unusual properties were studied. After suggested treatment they became luminescent and also
acquired a magnetic moment. Nanoparticles were prepared by laser pyrolysis of silane in a gas flow reactor followed by chemical
treatment in methanol (MeOH) + HF + FeCl3 solution. After the treatment. nanoparticles gained stable luminescence with the peak position dependence on the excitation
wavelength. With increasing of the excitation wavelength from 365 to 456 nm, the photoluminescent peak shifted from 632 to
665 nm. Luminescence of such nanoparticles had blue shift in comparison with the nanoparticles etched in widely-used solution
for the silicon—MeOH + HF + HNO3. Moreover, after such treatment the magnetic moment of nanoparticles appeared, which is not inherent for the as-prepared
nSi. Multifunctional silicon nanoparticles with both stable luminescence and magnetic moment at the same time are perspective
for biology and medicine use as the optical and magnetic markers. 相似文献
7.
许长谭 《光谱学与光谱分析》2001,21(4):438-440
应用三角晶场中d^2(d^8)电子组态包括静电相互作用和自旋-轨道耦合作用的强场能量矩阵,采用完全对角化方法,精确地计算了具有D3d对称的Ni^2 :CsMgCl3的光学吸收谱和EPR谱,理论结果与实验值符合得很好。 相似文献
8.
J.T. Kim 《Journal of Molecular Spectroscopy》2009,256(1):57-67
The potential energy curves, permanent and transition dipole moments as well as spin-orbit and angular coupling matrix elements between the KCs electronic states converging to the lowest three dissociation limits were evaluated in the basis of the spin-averaged wavefunctions corresponding to pure Hund’s coupling case (a). The quasi-relativistic matrix elements have been obtained for a wide range of internuclear distance by using of small (9-electrons) effective core pseudopotentials of both atoms. The core-valence correlation has been accounted for a large scale multi-reference configuration interaction method combined with semi-empirical core polarization potentials. The static dipole polarizabilities of the ground X1Σ+ and a3Σ+ states were extracted from the closed-shell coupled-cluster energies by the finite-field method. Among the singlet and triplet Σ+ states manifold the pronounced avoided crossing effect between repulsive walls of the (2,3)3Σ+ states has been discovered and analyzed by finite-difference calculation of radial coupling matrix elements. The resulting transition dipole moments and potentials were used to predict radiative lifetimes and emission branching ratios of excited vibronic states while the calculated angular coupling matrix elements were transformed to Λ-doubling constants of the (1,2)1Π states and magnetic g-factor of the ground state. The accuracies of the present results are discussed by comparing with experimental data and preceding calculations. 相似文献
9.
Electronic structures in coupled two quantum dots by 3D-mesh Hartree-Fock-Kohn-Sham calculation 总被引:2,自引:0,他引:2
T. Matsuse T. Hama H. Kaihatsu N. Toyoda T. Takizawa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):391-394
To study the electronic structures of quantum dots in the framework of self-interaction-free including three dimensional effects,
we adopt the theory of nonlocal effective potential introduced by Kohn and Sham [#!ks65!#]. For utilizing the advantageous
point of the real space (3D) mesh method to solve the original nonlinear and nonlocal Hartree-Fock-Kohn-Sham (HFKS)-equation,
we introduce a linearization of the equation in the local form by introducing the local Coulomb potentials which depend on
explicitly the two single particle states. In practice, for solving the local form HFKS-equation, we use the Car-Parrinello-like
relaxation method and the Coulomb potentials are obtained by solving the Poisson equation under proper boundary conditions.
Firstly the observed energy gap between triplet- and singlet-states of N = 4 in DBS [#!tarucha96!#] is discussed to reproduce the addition energies and chemical potentials depending the magnetic
field. Next the coupling between two-quantum dots in TBS [#!aht97!#] is studied by adding the square barrier between two dots.
The spin-degeneracy [#!aht97!#] measured in gate-voltage depending on magnetic field is well reproduced in the limit of small
mismatch. Finally, the electronic states in the ring structure are calculated and discussed how the ring size and magnetic
field affect to the structures.
Received 30 November 2000 相似文献
10.
Qing-Ping Wu Xing-Dao He Zheng-Fang Liu 《Physica E: Low-dimensional Systems and Nanostructures》2011,44(3):738-742
Spin precession formula is deduced in graphene with Rashba spin-orbit coupling (RSOC) and exchange field, which can control accurately the transmission of up-spin and down-spin electrons. And a wide-angle spin filter can be achieved by the combined effects of exchange field and RSOC. Further spin polarization can be observed, which increases with increasing RSOC or exchange field. 相似文献
11.
The solid state exhibits a fascinating variety of phases, which can be stabilized by the variation of external parameters such as temperature, magnetic field and pressure. Until recently, numerical analysis of magnetic and/or orbital phases with collective excitations on a periodic lattice tended to be done on a case-by-case basis. Nowadays dynamical matrix diagonalization (DMD) has become an important and powerful standard method for the calculation of dispersive modes. The application of DMD to the interpretation of inelastic neutron scattering (INS) data on dispersive magnetic excitations is reviewed. A methodical survey of calculations employing spin-orbit and intermediate coupling schemes is illustrated by examples. These are taken from recent work on rare earth, actinide and transition metal compounds and demonstrate the application of the formalism developed. 相似文献
12.
H. Nakamura N. Hayashi N. Nakai M. Okumura M. Machida 《Physica C: Superconductivity and its Applications》2009,469(15-20):908-911
In order to resolve a discrepancy of the magnetic moment on Fe between the experimental and calculation results, we perform first-principle electronic structure calculations for iron-based superconductors LaFeAsO1-xFx in which x=0.0 and x=0.125 by using the LSDA + U framework. Consequently, we confirm in both the mother and doped compounds that negative U correction is crucial in matching the calculated magnetic moment with the observed one. A reason of the negative correction is that the Coulomb interaction on Fe orbitals is unexpectedly screened than LSDA’s expectation. We discuss which type of situation emerges when the negative U is a good correction in these compounds. 相似文献
13.
J. Sjakste V. Tyuterev N. Vast 《Applied Physics A: Materials Science & Processing》2007,86(3):301-307
Interactions between excited electrons and short-wavelength (intervalley) phonons in GaAs are studied using density functional
theory for the conduction bands, and density functional perturbation theory for phonon frequencies and matrix elements of
the electron–phonon interaction. We have calculated the deformation potentials (DPs) and the average intervalley scattering
time 〈τ〉. The integration of the scattering probabilities over all possible final states in the Brillouin zone has been performed
without any ad hoc assumption about the behavior of the electron–phonon matrix elements nor the topology of the conduction
band. For transitions from the L point to Γ valley (within the first conduction band), we find 〈τ〉L to be 1.5 ps at 300 K, in good agreement with time-resolved photoluminescence experiment. We discuss the difference between
our calculated DPs, and effective parameters used in Monte Carlo simulations of optical and transport properties of semiconductors.
The latter are based on Conwell’s model, in which electron–phonon interaction is described by one single constant and a parabolic
model is used for conduction bands. We deduce the effective DP from our 〈τ〉, and compare it to our calculated DPs. We conclude
that only effective DPs obtained from a full calculation of 〈τ〉 are relevant parameters for Monte Carlo simulations.
PACS 71.10-w; 72.10.Di; 71.55.Eq 相似文献
14.
Theory of Raman scattering of light on spin-flip and electronic excitation in Europium chalcogenides
The inelastic scattering of light in magnetic semiconductors from the family of the Europium chalcogenides is discussed in relation with spin-orbit coupling and d-f exchange interaction. It is shown that the Raman processes connected with spin-flip and other electronic excitations can occur in the energy range of 0.1-0.5 eV. In this case and for the typical values of d-f exchange interaction and spin-orbit coupling parameter lying between 0.05 and 0.1 eV, the values of the differentional cross-sections are between 10-9 - 10-11 cm2sr-1 sec. The selection rules for the polarization of the incident and scattered photons as well as the Raman tensors for the four allowed transitions are derived. The possibility of applying spin-flip Raman processes in magnetic semiconductors in the tuning of electromagnetic radiation in Raman lasers is analyzed briefly. 相似文献
15.
Theoretical study of the electronic structure of LiNa and LiNa<Superscript>+</Superscript> molecules
Neji Khelifi Riadh Dardouri Omar Marzook Al-Dossary Brahim Oujia 《Journal of Russian Laser Research》2009,30(2):172-186
Adiabatic potential energy, spectroscopic constants, dipole moments, and vibrational levels of the lowest electronic states
of the alkali dimer LiNa molecule dissociating into Na (3s, 3p, 4s, 3d, and 4p) + Li (2s, 2p, 3s, and 3p) in 1,3Σ, 1,3Π, and 1,3Δ symmetries are presented. Adiabatic results are also reported for 2Σ, 2Π, and 2Δ electronic states of the molecular ion LiNa+ dissociating into Li (2s, 2p, 3s, and 3p) + Na+ and Li+ + Na(3s, 3p, 4s, 3d, and 4p). We use an ab initio approach involving a non-empirical pseudopotential for the Li (1s2) and Na (1s22s22p6) cores and core valence correlation correction. A very good agreement is obtained for some lowest states of the LiNa and
LiNa+ molecules for spectroscopic constants with the available theoretical works. The existence of numerous avoided crossings between
electronic states of 2Σ and 2Π symmetries is related to the charge transfer process between the two ionic systems Li+Na and LiNa+. 相似文献
16.
First-principle self-consistent full potential linear augmented plane wave calculations based on density functional theory using hybrid functional PBE0 are performed to study magnetic moments, density of states and half-metallicity of L21 type full Heusler alloys with formula Co2Y Si. Y is Ti, V, Mn and Fe. We have compared these results with those of the PBE-GGA exchange correlation functional and the LDA + U method. The results for Co2FeSi and Co2MnSi are completely different; using the PBE0 hybrid functional for Co2FeSi predicts experimental magnetic moment and also predicts this material to be half-metallic ferromagnet, while using PBE-GGA predicts it not to be half-metal. The results of PBE0 are more similar to the ones obtained by LDA + U method. 相似文献
17.
S. P. Sadykova W. Ebeling I. M. Tkachenko 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(1):117-130
The electron-electron, electron-ion, ion-ion and charge-charge static structure factors are calculated for alkali
(at T = 30 000 K, 60 000 K, n
e
= 0.7 × 1021 ÷ 1.1 × 1022 cm-3) and Be2+ (at T = 20 eV,
n
e
= 2.5 × 1023 cm-3) plasmas using the method described by Gregori et al. The dynamic structure factors for alkali plasmas are calculated at
T = 30 000 K, n
e
= 1.74 × 1020, 1.11 × 1022 cm-3 using the method of moments developed by Adamjan et al. In both methods the screened Hellmann-Gurskii-Krasko potential, obtained
on the basis of Bogolyubov's method, has been used taking into account not only the quantum-mechanical effects but also the
repulsion due to the Pauli exclusion principle. The repulsive part of the Hellmann-Gurskii-Krasko (HGK) potential reflects
important features of the ion structure. Our results on the static structure factors for
Be2+ plasma deviate from the data obtained by Gregori et al., while our dynamic structure factors are in a reasonable agreement
with those of Adamyan et al.: at higher values of k and with increasing k the curves damp down while at lower values of k, and especially at higher electron coupling, we observe sharp peaks also reported in the mentioned work. For lower electron
coupling the dynamic structure factors of Li+, Na+, K+, Rb+ and Cs+ do not differ while at higher electron coupling these curves split. As the number of shell electrons increases from Li+ to Cs+ the curves shift in the direction of low absolute value of ω and their heights diminish. We conclude that the short range forces, which we take into account by means of the HGK model
potential, which deviates from the Coulomb and Deutsch ones, influence the static and dynamic structure factors significantly. 相似文献
18.
Determination of the optimal parameters for the fabrication of ZnO thin films prepared by spray pyrolysis method 总被引:1,自引:0,他引:1
In this work, ZnO thin films have been prepared by spray pyrolysis deposition method on the glass substrates. The effect of
deposition parameters, such as deposition rate, substrate temperature and solution volume has been studied by X-ray diffraction
(XRD) method, UV–Vis–NIR spectroscopy, scanning electron microscopy (SEM), and electrical measurements. The XRD patterns indicate
polycrystalline wurtzite structure with preferred direction along (0 0 2) planes. Thin films have transparency around 90%
in the visible range. The optical band gap was determined at 3.27 eV which did not change significantly. Evolution of electrical
results containing the carriers’ density, sheet resistance and resistivity are in agreement with structural results. All the
results suggest the best deposition parameters are: deposition rate, R = 3 ml/min, substrate temperature, T
s = 450°C and thickness of the thin films t = 110–130 nm. 相似文献
19.
基于相关一致极化4zeta(aug-cc-pVQZ)基组, 应用量子化学从头计算中高水平的多参考组态相互作用方法计算了BCl+ 两个离解极限B+(1Sg)+Cl(2Pu)和B (2Pu)+Cl+ (3Pg)的14个Λ-S态势能曲线. 在计算中考虑了Davidson修正(+Q)和标量相对论效应, 并首次在计算中考虑了BCl+ 的旋轨耦合效应, 获得了由能量最低的4个Λ-S态分裂出的7个Ω 态. 计算结果表明相同对称性的Ω 态的势能曲线存在着非常明显的避免交叉. 通过分析Λ-S态的电子结构, 得到了各态的电子跃迁特性, 并确认了电子态的多组态性质. 使用LEVEL程序通过求解径向的Schrödinger方程得到了束缚Λ-S 和Ω态的光谱参数De, Re, Te, ωe, ωeχe和Be. 通过和已有的Λ-S态X2∑+ 的实验数据进行对比发现, 本文所得的计算结果与实验结果非常一致. 而文中其他电子态的光谱参数均为首次报道.
关键词:
势能曲线
光谱参数
多参考组态相互作用方法
旋轨耦合 相似文献
20.
The electronic structure and magnetic properties of PuMGa5 compounds (M = Co, Fe, Ni, Rh, Ir) have been calculated within the LDA + U + SO method taking into account the strong electron-electron correlations and the spin-orbit coupling in the 5f shell of the actinide metal. The features of the electronic structure, coupling type, electron configuration, and magnetic state of the plutonium ion have been considered depending on the type of transition metal in PuMGa5. The estimates of the effective magnetic moment of the plutonium ion agree well with the known experimental values. It has been shown that the occupancy of d states of the transition metal correlates with the appearance of superconductivity in the compounds of this class, providing the optimum doping regime in the electronic subsystem. 相似文献