Zeroth-order polarization propagator

A full relativistic theory for coupling tensors within the polarization propagator approach at the RPA level was presented as a generalization of the nonrelativistic theory. Relativistic calculations using the PP formalism have three requirements, namely (i) all operators representing perturbations must be given in relativistic form (ii) the zeroth-order Hamiltonian must be the Dirac-Coulomb-Breit Hamiltonian, /foBC, or some approximation to it and (iii) the electronic states must be relativistic spin-orbitals within the particle-hole or normal ordered representation. Aucar and Oddershede used the particle-hole Dirac-Coulomb-Breit Hamiltonian in the no-pair approach as a starting point, Eq. (18),... 

The GOA has been widely used in the study of light propagation in photoelastic materials and liquid crystals. Recently, Ong and Meyer presented a general GOA formalism for wave propagation in optically inhomogeneous, planar, uniaxial media and found excellent agreement between the zeroth-order GOA and the exact solution for the case of a periodically bent nematic liquid crystal. The approach of Ong and Meyer, however, is restricted to linearly polarized light in planar structures. 

We have shown that the zeroth-order geometric optics approximation can be used to describe the propagation of normally incident, elliptically polarized light in an inhomogeneous, locally uniaxial medium. The approximation corresponds to finding an asymptotic solution of the wave equation in the short-wavelength limit. It is found that a set of pseudo-Stokes parameters, linearly related to the usual Stokes parameters, can be defined to characterize the propa-... 

Relativistic calculations of NMR properties of RgH ion (where Rg = Ne, Ar, Kr, Xe), Pt shielding in platinum complexes, and Pb shielding in solid ionic lead(II) halides have been reported in this review period. For the Rg nucleus in the RgH ions, the following methods were used and results compared with each other non-relativistic uncorrelated method (HF), relativistic uncorrelated methods, four component Dirac Hartree-Fock method (DHF) and two-component zeroth order regular approach (ZORA), non-relativistic correlated methods using second order polarization propagator approach SOPPA(CCSD), SOPPA(MP2), respectively coupled cluster singles and doubles or second order Moller-Plesset, and... 

Going one step further and retaining only the zeroth-order contribution to the hessian matrix, i.e. brings us back to the frequency-dependent version of uncoupled Hartree-Fock, Eq. (10.5), sometimes also called the zeroth-order polarization propagator approximation (ZOPPA). 

In SOPPA the equations for the polarization propagator are solved by retaining all terms second order in the fluctuation potential. The reference state is a correlated Moller Plesset wavefunction with the corresponding correlation coefficients. The zeroth-order wavefunction is a single reference SCF ground state. Correlation is introduced via the fluctuation potential. SOPPA includes dynamical correlation, but not nondynamical effects. The same technique can be applied to other methods, e.g., coupled cluster, giving CCSDPPA where the cluster amplitudes replace the correlation coefficients used in SOPPA. 

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