Ab initio calculation of spin-orbit coupling constants for gaussian lobe and gaussian-type wave functions

The spin-orbit coupling constants of a series of diatomic compounds containing first row atoms have been calculated using ab initio molecular wave functions with gaussian lobe and gaussian-type basis sets. In most cases, fair agreement with the experimental values has been achieved. It is pointed out that multicentre terms have almost no effect on the spin-orbit coupling constant. Furthermore, suggestions for a one-electron approximation using effective nuclear charges are presented.     

Ab initio calculation of the spin-orbit coupling constant from gaussian lobe SCF molecular wavefunctions

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.     

A New Determination of the Lambda-Nucleon Coupling Constants in Relativistic Mean Field Theory

A new determination of the Lambda-nucleon coupling constants in relativistic mean field theory is presented by optimizing both hyperon binding energy and spin-orbit splitting.Hypernuclear single particle spectra with the new coupling constants suggest the good agreement between the calculation and available data.The spin-orbit splitting of hyperon in medium mass hypernuclei is systematically larger than that in light-or heavy-mass hypernuclei.The sensitivity of the Lambda spin-orbit splitting to the omega-Lambda-Lambda tensor coupling term is also explored.     

Intramolecular interactions and deuteration effect in nonradiative deactivation of lowest triplet state of anthracene and naphthalene

In the approximation of nonadiabatic interactions and considering all out-of-plane vibrational modes to be promoting ones, we calculate changes in the rate constants T _s K _dg ^s of the nonradiative degradation T ₁ ^s ⇝ S ₀ of in-plane spin (s) triplet states as a result of the complete deuteration of anthracene and naphthalene molecules. We examine how the deuteration, the frequency factor, and the shape of promoting vibrational modes affect the squared matrix elements of both nonadiabatic coupling and adiabatic vibronically induced spin-orbit (VISO) coupling of electronic states. The compensation effect of spin-orbit interactions in structural elements of the carbon backbone of the anthracene molecule is ascertained.     

A New Determination of the Lambda-Nucleon Coupling Constants in Relativistic Mean Field Theory

A new determination of the Lambda-nucleon coupling constants in relativistic mean field theory is presented by optimizing both hyperon binding energy and spin-orbit splitting. Hypernuclear single particle spectra with the new coupling constants suggest the good agreement between the calculation and available data. The spin-orbit splitting of hyperon in medium mass hypernuclei is systematically larger than that in light- or heavy-mass hypernuclei. The sensitivity of the Lambda spin-orbit splitting to the omega-Lambda-Lambda tensor coupling term is also explored.     

Einfluß einer Quasiteilchen-Spinbahnwechselwirkung auf die magnetischen Momente leichter Atomkerne

Using Migdal's theory of interacting quasiparticles, the influence of a two-body spin-orbit interaction in addition to the spin-spin interaction on magnetic moments of nuclei was investigated in the mass regionA=11 toA=65. The coupling constants of the spin-orbit interaction were determined from spin-orbit splittings of single particle energies, and those of the spin-spin interaction were adjusted by fitting magnetic moments. The constants of the spin-spin interaction were found to be dependent on the mass value. The inclusion of the spin-orbit interaction led to a better agreement of theoretical and experimental magnetic moments of light nuclei. The spin-orbit contribution was averaged 7% over all nuclei, but reached 20–30% for some of them.     

Spin-orbit coupling constant and <r −3> in transuranic ions

The spin-orbit coupling parameter ζ, the quantum average <r ^?3>, and binding energy ? E for atomic number Z = 92, 94, 96 and net ionic charge approximately 1 and 5, have been calculated for the 5f electrons. The potential assumed in the one-electron wave function calculation is that given by the Thomas-Fermi model of a positive ion.

It is shown that the ratio ζ/<r ^?3> is fairly insensitive to changes in the surroundings of the ion, and can be used for estimating one of the parameters with the experimental value of the other.

The 5g electrons are shown to be effectively free in the considered range of Z and n.

The behaviour of the wave function as a function of n and Z is discussed.     

Inelastic life-time of the conduction electrons in some noble metal films

Magneto-conductance measurements of thin films of Cu, Ag and Au are reported. The measurements are evaluated with the theory of weak localization and yield for the noble metals a very good agreement with the theory in the whole field range up to 5T. No adjustment of the theoretical prefactor is necessary. The magneto-conductance curves show a pronounced structure caused by spin-orbit coupling. The measurements yield the inelastic life-time and the spin-orbit coupling of the conduction electrons for Cu, Ag and Au. _i obeys a 1/T ^p law withp=1.65.     

Note on the theory of dissociation pressures of gas hydrates

Couplings over four bonds, ⁴ J _HH, are discussed for compounds where stereochemistry is thought to be the dominant factor determining their values. A simple MO theory [3, 4] provides calculated coupling constants in agreement with experiment. The form of the theory permits an analysis of the mechanisms responsible for long-range coupling. The approach is generalized to include distorted cyclohexane fragments and these results are presented in a graphical form.     

A theoretical study of the spectroscopic states of the CF molecule

LCAO-MO SCF calculations on the ground and excited states of CF are described. Close agreement with observed term values is obtained. The calculation of some molecular properties is discussed, and a very good result is obtained for the spin-orbit coupling in the ground state. The positive spin-orbit coupling in the ²Δ state is not explained. It is shown that the observed predissociation in the A state must be attributed to a curve crossing at a smaller internuclear distance than equilibrium, and that the ⁴Σ^- state from 5σ 2π² is responsible. Calculations show that a second-order treatment of the A ²Σ⁺-⁴∑^- interaction is necessary and sufficient to account for the predissociation.     

尺寸相关的弹性常数对应变硅纳米线电学性质的影响

从Keating模型出发,基于离散化思想建立了计算单晶硅纳米线弹性常数和杨氏模量的半连续原子晶格力学模型. 从微扰理论和形变势理论出发,采用有限差分方法建立了计算不同晶向应变硅纳米线价带结构的数值模型. 结合上述的两个计算模型,进而应用经典弹道传输模型研究了轴向应力和弹性常数对p型硅纳米线弹道晶体管电学特性的影响. 研究结果表明,硅纳米线的弹性常数和杨氏模量呈现尺寸效应,该结果与分子动力学的模拟结果具有很好的一致性. 同时发现尺寸相关的弹性常数对硅纳米线晶体管输运电流的影响强烈依赖于单轴应力对输运电流的影 关键词： 应变硅纳米线 弹性常数 弹道电流 价带结构模型     

自旋轨道耦合作用对碳纳米管电子能带结构的影响

本文考虑自旋轨道耦合作用的情况下,采用紧束缚近似螺旋对称模型计算了单壁碳纳米管的电子能带结构.研究发现:对于Armchair型单壁碳纳米管,自旋轨道耦合作用和弯曲效应共同导致了费米面Dirac点附近电子能带结构的能隙;对于Zigzag型和手性单壁碳纳米管,自旋轨道耦合作用使得电子最高占据态和最低未占据态产生能级劈裂,能级劈裂的大小不但与碳纳米管的直径和手性角密切相关,而且相对于费米面是不对称的;根据指数(n,m)可以将Zigzag型和手性单壁碳纳米管分为金属性碳纳米管(ν=0) 关键词： 单壁碳纳米管 自旋轨道耦合 紧束缚近似螺旋对称模型     

A matrix method for the calculation of nonlocal exchange potential and spin-orbit coupling in the first-principles calculation method

Adequate treatment of exchange interaction and inclusion of spin-orbit coupling are important in obtaining reliable electronic structures of semiconductors and magnetic materials. Here, a matrix method has been derived to calculate nonlocal exchange potential and spin-orbit coupling within a muffin-tin-orbital based first-principles calculation method. Good agreement between calculated and experimental band gaps for various zinc-blende and wurtzite semiconductors demonstrated that direct calculation of nonlocal exchange potential is feasible. This method may be an improvement over the currently used LSDA  +  U or LSDA  +  GGA  +  U method, which uses an adjustable U parameter, for wide-band-gap semiconductors and magnetic materials. In this method, the use of an extended Hamiltonian matrix, which contains off-diagonal matrix elements between up- and down-spin states due to spin-orbit coupling, enables mutual adjustment of the occupation of up- and down-spin states through atomic orbitals. In contrast, in the conventional spin-polarized calculation method up- and down-spin sub-matrices are diagonalized separately. The calculated spin-orbit splitting for the triplet states at the Γ point for GaAs and ZnS are in good agreement with experimental data.     

Quantum theory of the magneto-optical effect and magnetization of Nd-substituted yttrium iron garnet

The magneto-optical and magnetic properties of Nd ³⁺ ions in Y ₃Fe ₅O ₁₂ garnet are analyzed by using quantum theory. In the spontaneous state, the magneto-optical effects originate mainly from the intra-ionic electric dipole transitions between the 4 f ³ and 4 f ²5d states split by the spin-orbit, crystal field, and superexchange interactions. For the excited configuration, the coupling scheme of Yanase is extended to the Nd ³⁺ ion. The magneto-optical resonance frequencies are mainly determined by the splitting of the 5d states induced by the crystal field. The theoretical results of both Nd magnetization and Faraday rotation are in good agreement with experiments. The observed Faraday rotation is proved to be of the paramagnetic type. Although the value of the magneto-optical resonance frequency derived from a macroscopic analysis is approximately confirmed by our theoretical study, a new assignment about the transitions associated with this resonance is unambiguously determined. The spin-orbit coupling of the ground configuration has a great influence on both the Faraday rotation and magnetization, but, unlike the theoretical results obtained in some metals and alloys, the relation between the Faraday rotation and the spin-orbit coupling strength is more complex than a linear one. The magnitude of the magneto-optical coefficient increases as the spin-orbit interaction strength of the ground configuration decreases when the strength is not very weak. Finally, the temperature dependence of the magneto-optical coefficient and the effect of the mixing of different ground-term multiplets induced by the crystal field are analyzed. Received 8 November 2000     

An ab initio study of the hyperfine structure in the X2 Π electronic state of HCCS–calculation of vibronically averaged components of the anizotropic hyperfine tensor

The results of ab initio calculations of the vibronically averaged components of the anisotropic magnetic hyperfine tensor in the low-lying vibronic species of the X²Π electronic state of the HCCS radical are reported. The electronically averaged hyperfine coupling constants for hydrogen, deuterium, ¹³C and ³³S are obtained as functions of two bending vibrational modes by the density functional theory method. The vibronic wave functions are calculated with the help of a variational approach which takes into account the Renner–Teller effect and spin-orbit coupling. The results of ab initio calculations are compared to the corresponding experimental findings.     

Spin-orbit effects in leed from Ni(001): experiment and theory

A polarized-electron gun based on photoemission from a molecular beam epitaxy-grown GaAs(001) surface has been used to study spin-orbit-induced scattering asymmetries from a paramagnetic Ni(001) surface well above the Curie temperature. Asymmetry versus energy data of the specular beam are compared with corresponding theoretical results obtained for different ion-core scattering potentials. The good agreement between experiment and theory suggests that spin-polarized low energy electron diffraction can be useful also for low-Z surfaces, for which spin-orbit coupling is small.     

The calculation of fluorine hyperfine interactions in π-electron radicals

Q factors have been calculated for fluorine hyperfine interaction in π-electron radicals using an independent-electron model for the σ orbitals. It is shown that the off-diagonal elements give an important contribution to fluorine coupling constants. Combining these Q factors with calculated π-electron spin densities of fluoro-nitrobenzenes gives good agreement with experimental coupling constants.     

Theoretical study of the electron paramagnetic resonance parameters and local structure for the tetragonal Ir<Superscript>2+</Superscript> centre in NaCl

The electron paramagnetic resonance (EPR) parameters (the g factors, hyperfine structure constants and the superhyperfine parameters) for the tetragonal Ir²⁺ centre in NaCl are theoretically investigated from the perturbation formulas of these parameters for a 5d⁷ ion in tetragonally elongated octahedra. This impurity centre is attributed to the substitutional [IrCl₆]⁴⁻ cluster on host Na⁺ site, associated with the 4% relative elongation along the C ₄-axis due to the Jahn-Teller effect. Despite the ionicity of host NaCl, the [IrCl₆]⁴⁻ cluster still exhibits moderate covalency and then the ligand orbital and spin-orbit coupling contributions should be taken into account. In addition, the theoretical EPR parameters based on the Jahn-Teller elongation show good agreement with the observed values.     

Crystal field analysis of the one-dimensional antiferromagnet CsCoCl3

In the past quadrupole splitting data for⁵⁷Fe doped CsCoCl₃ has been fitted to a model with crystal fields and spin-orbit coupling for T>T _N1. However there is poor agreement with data below T _N1. In this paper the results of attempting to refit the data over all temperatures, and the effects of the orbit lattice interaction are reported.     

Calculation of potential energy curves for Rb2 including relativistic effects

All-electron relativistic calculations have been performed on the Rb₂ molecule. The molecular orbitals are optimized within a spin-free no-pair Hamiltonian formalism and spin-orbit coupling is treated using quasi-degenerate perturbation theory. Potential curves of the ground state and several excited states are calculated, and the spectroscopic constants T _e, D _e, R _e and ω_e are in good agreement with experimental values. The spin-orbit splittings at the 5p and 6p asymptotic limits are found to be underestimated by about 30%. Large perturbations in the spectra from the 1¹Σ⁺ _u(A) state are predicted due to an avoided crossing with a 1 ³Π_ub state caused by spin-orbit interaction. The predissociation dynamics of the 2 ¹Π_uC and 3 ¹Π_uD states is discussed. The calculations support the observation that a (1) ³ Δ_u state causes the fast predissociation of the ^{3 1}Π_uD state but rule out the (2)³Σ⁺ _u state as causing the slow predissociation at the lower part of the 3 ¹Π_uD potential energy curve.