Relativistic spin-orbit operator

Scalar relativistic DKH2 approach with Pauli spin-orbit operator, reported in [ 114] with respect to WF6... 

Most common among the approximate spin-orbit Hamiltonians are those derived from relativistic effective core potentials (RECPs).35-38 Spin-orbit coupling operators for pseudo-potentials were developed in the 1970s.39 40 In the meantime, different schools have devised different procedures for tailoring such operators. All these procedures to parameterize the spin-orbit interaction for pseudo-potentials have one thing in common The predominant action of the spin-orbit operator has to be transferred from... 

Teichteil et al.41 fit a spin-orbit pseudo-operator such that its action on a pseudo-orbital optimally reproduces the effect of the true spin-orbit operator on the corresponding all-electron orbital. Ermler, Ross, Christiansen, and co-workers42 9 and Titov and Mosyagin50 define a spin-orbit operator as the difference between the and j dependent relativistic effective pseudopotentials (REPs)51... 

Ab Initio Relativistic Effective Potentials with Spin-Orbit Operators. II. K through Kr. 

J. Chem. Phys., 93, 6654 (1990). Ab Initio Relativistic Effective Potentials with Spin-Orbit Operators. IV. Cs through Rn. 

Relativistic Effective Potentials with Spin—Orbit Operators. VII. Am through Element 118. 

Configuration Interaction Using the Graphical Unitary Group Approach and Relativistic Core Potential and Spin—Orbit Operators. 

Another method, devised by Cohen et al. to determine oxygen-rate gas collision parameters is to define an effective spin-orbit operator that includes r dependence, Zeff/r3, where the value of Zeff is adjusted to match experimental data (76). Langhoff has compared this technique with all-electron calculations using the full microscopic spin-orbit Hamiltonian for the rare-gas-oxide potential curves and found very good agreement (77). This operator has also been employed in REP calculations on Si (73), UF6 (78), U02+ and Th02 (79), and UF5 (80). The REPs employed in these calculations are based on Cowen-Griffin atomic orbitals, which include the relativistic mass-velocity and Darwin effects but do not include spin-orbit effects. Wadt (73), has made comparisons with calculations on Si by Stevens and Krauss (81), who employed the ab initio REP-based spin-orbit operator of Ermler et al. (35). 

Fig. 6. Average relativistic effective core potential and relativistic effective core potential energy curves for two states of Bi2. HF, Hartree-Fock GVB(pp), eight-configuration perfect-pairing generalized valence bond FVCI, full-valence Cl based on the GVB(pp) wave functions FV7R, full-valence Cl plus single and double promotions to virtual MOs relative to seven-dominant configurations. (The FVCI and FV7R calculations include the REP-based spin-orbit operator.)...

An accurate procedure for performing calculations that incorporate spin-orbit and other relativistic effects, and that represents intermediate coupling states for molecules containing heavy atoms, is based on A-S coupling in conjunction with the use of the ab initio REP-based spin-orbit operator and extended configuration interaction. The coupling scheme is more familiar than co-co coupling to chemists and physicists. In addition, the complexity of calculations necessary to achieve reliable results is computationally tractable. 

R.B. Ross, J.M. Powers, T. Atashroo, W.C. Ermler, L.A. LaJohn, P.A. Christiansen, Ab initio relativistic effective potentials with spin-orbit operators. IV. Cs through Rn. J. Chem. Phys. 93, 6654-6670, 1990. 

The nonrelativistic limit of this operator yields the paramagnetic spin-orbit (PSO) contribution of Ramsey s theory. The remaining terms in eq. (4.10b) result in the ZORA relativistic spin-orbit Hamiltonian,... 

Shape-consistent pseudopotentials including spin-orbit operators based on Dirac-Hartree-Fock AE calculations using the Dirac-Coulomb Hamiltonian have been generated by Christiansen, Ermler and coworkers [161-170]. The potentials and corresponding valence basis sets are also available on the internet under http //www.clarkson.edu/ pac/reps.html. A similar, quite popular set for main group and transition elements based on scalar-relativistic Cowan-Griffin AE calculations was published by Hay and Wadt [171-175]. 

True relativistic ab initio calculations have been done for hydride molecules such as T1H (Pyykko and Desclaux, 1976) and have been extended to heavy nonhydride molecules, such as I2 (de Jong, et ai, 1997). Other types of calculations involve treating the spin-orbit operator as a perturbation and adding its effects to the nonrelativistic potential curves (for example, Ne2, Cohen and Schneider, 1974 LiHg, Gleichmann and Hess, 1994). 

Another possibility is to include the relativistic operators and IP ) in the Hamiltonian during the variational determination of wave function. There are two entry points at which a vEU iationally stable spin-orbit operator can be added to the nonrelativistic Hamiltonian. 

The Amsterdam Density Functional (ADF) method [118,119] was used for calculations of some transactinide compounds. In a modem version of the method, the Hamiltonian contains relativistic corrections already in the zeroth order and is called the zero-order regular approximation (ZORA) [120]. Recently, the spin-orbit operator was included in the ZORA Fock operator [121]. The ZORA method uses analytical basis fimctions, and gives reliable geometries and bonding descriptions. For elements with a very large SO splitting, like 114, ZORA can deviate from the 4-component DFT results due to an improper description of the pi/2 spinors [117]. Another one-component quasirelativistic scheme [122] applied to the calculations of dimers of elements 111 and 114[116,117]isa modification of the ZORA method. 

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