Brueckner orbitals, Dyson orbitals, and correlation potentials

Ortiz, J. V.

doi:10.1002/qua.20204

Cited by 48 publications

(54 citation statements)

References 19 publications

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“…However, without much extra effort or loss of generality the same approach can be applied to Dyson orbitals that include correlation and relaxation effects. 13,14,33 Photodetachment from a one-electron mixed state described by Eq. (3) will generally yield s, p, and d electricdipole allowed partial waves via the s → p and p → s, d transitions.…”

Section: Hanstorp's Approximationmentioning

confidence: 99%

Photodetachment anisotropy for mixed s-p states: 8/3 and other fractions

Sanov

Grumbling

Goebbert

et al. 2013

The Journal of Chemical Physics

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An approximate model for analytical prediction of photoelectron angular distributions in anion photodetachment from mixed s-p states is presented. Considering the dipole-allowed s, p, and d free-electron partial waves, the model describes photodetachment anisotropy in terms of the fractional p character of the initial orbital and the A and B coefficients describing the relative intensities of the p → d to p → s and s → p to p → s channels, respectively. The model represents an extension of the central-potential model to an intermediate regime encompassing varying degrees of s and p contributions to the initial bound orbital. This description is applicable to a broad class of hybrid molecular orbitals, particularly those localized predominantly on a single atom. Under the additional assumption of hydrogenic or Slater-type orbitals, the B/A ratio in photodetachment from a mixed 2s-2p state is shown to equal 8/3. Corresponding fractions are derived for other ns-np mixing cases. The predictions of the model are tested on several anion systems, including NH(2)(-) and CCl(2)(-). The quantitative discrepancies in the latter case are attributed to the breakdown of the central-atom approximation and a mechanism for corresponding corrections is indicated.

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Section: Hanstorp's Approximationmentioning

confidence: 99%

Photodetachment anisotropy for mixed s-p states: 8/3 and other fractions

Sanov

Grumbling

Goebbert

et al. 2013

The Journal of Chemical Physics

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“…We have used the Van Leeuwen and Baerends [3] potential (LB94), which introduces a gradient correction to the local density approximation exchange correlation so as to reproduce correctly the Coulomb asymptotic behavior of the potential. It reproduces KS MO negative energies [1,4,5] nearly equal to the ionization potentials (IP) obtained from photoelectron spectra, which are only accurately given normally by many-body Dyson orbitals [6]. The bond length has been set to its experimental [7-10] value, i.e., OCS bonds length are CS = 0.156 nm, CO = 0.1157 nm, and CS = 0.155 nm for CS 2, and these molecules are oriented along the z axis.…”

mentioning

confidence: 99%

Nonperturbative time-dependent density-functional theory of ionization and harmonic generation in OCS and CS2molecules with ultrashort intense laser pulses: Intensity and orientational effects

Fowe

Bandrauk

2011

Phys. Rev. A

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Molecular high-order harmonic generation (MHOHG) and molecular orbital ionization rates are calculated for the nonsymmetric OCS and symmetric CS 2 molecules using numerical solutions of Kohn-Sham (KS) equations of time-dependent density functional theory in the nonlinear nonperturbative regime of laser-molecule interactions for different laser-molecule orientations and intensities. It is found that the ionization of inner-shell KS molecular orbitals contributes significantly to the ionization and MHOHG processes for intensities I 3.5 × 10 14 W/cm 2 . Ionization rate maxima correspond to the alignment of maximum KS orbital densities with the laser pulse polarization instead of orbital ionization potentials. Furthermore, degeneracies of orbitals are removed as a function of laser-molecule angle, thus affecting ionization rates, the MHOHG spectra, and their polarizations, the latter allowing for identifying inner-orbital ionization.We report in this paper the nonlinear nonperturbative response to short (few cycles) intense laser pulses of the nonsymmetric OCS and symmetric CS 2 molecules. The timedependent density functional theory (TDDFT) Kohn-Sham (KS) equation for each occupied molecular orbital (MO) in these molecules was discretized in space using finitedifference (FD) grid techniques as reported earlier for CO 2 and other molecules [1,2]. We have used the Van Leeuwen and Baerends [3] potential (LB94), which introduces a gradient correction to the local density approximation exchange correlation so as to reproduce correctly the Coulomb asymptotic behavior of the potential. It reproduces KS MO negative energies [1,4,5] nearly equal to the ionization potentials (IP) obtained from photoelectron spectra, which are only accurately given normally by many-body Dyson orbitals [6]. The bond length has been set to its experimental [7-10] value, i.e., OCS bonds length are CS = 0.156 nm, CO = 0.1157 nm, and CS = 0.155 nm for CS 2, and these molecules are oriented along the z axis. The time-dependent ionization probability P i,σ (t) of an individual spin-orbital is calculated [2] aswhere N i,σ (t) = ψ i,σ (r,t)|ψ i,σ (r,t) is the time-dependent population (survival probability) of the i,σ th spin population. The number of electrons inside the grid of volume V and remaining population arewhere n(r,0) = 2 N σ i |ψ iσ (r,0)| 2 is the total number of electrons in the initial state (without external field). The total ionization yield probability γ (t f ), computed at the final time t f of the propagation, is then obtained from the difference between initial and final probability β(t f ) in Eq. (2) and * andre.bandrauk@usherbrooke.ca tabulated in Table I for different laser-molecule angles θ and intensities.The power spectrum of the dipole accelerationd z (t) in a given direction yields the predicted MHOHG spectra [11,12] Recent work has shown that the most accurate method for generating the MHOHG spectra when dealing with molecular systems [5,11,12] is to calculate the dipole acceleration d z (t) from the exact time-dependent fu...

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“…The first Brueckner‐doubles, triple field‐operator method (BD‐T1)6,50–54 neglects the 2hp–2ph couplings that appear first in second order and, as in the NR2 method, obtains electron binding energies through diagonalization of a Hermitized matrix. The BD‐T1 method has proven to be remarkably versatile.…”

Section: Self‐energy Approximationsmentioning

confidence: 99%

Electron propagator theory: an approach to prediction and interpretation in quantum chemistry

Ortiz

2012

WIREs Comput Mol Sci

191

194

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Electron propagator theory provides a practical means of calculating electron binding energies, Dyson orbitals, and ground‐state properties from first principles. This approach to ab initio electronic structure theory also facilitates the interpretation of its quantitative predictions in terms of concepts that closely resemble those of one‐electron theories. An explanation of the physical meaning of the electron propagator's poles and residues is followed by a discussion of its couplings to more complicated propagators. These relationships are exploited in superoperator theory and lead to a compact form of the electron propagator that is derived by matrix partitioning. Expressions for reference‐state properties, relationships to the extended Koopmans's theorem technique for evaluating electron binding energies, and connections between Dyson orbitals and transition probabilities follow from this discussion. The inverse form of the Dyson equation for the electron propagator leads to a strategy for obtaining electron binding energies and Dyson orbitals that generalizes the Hartree–Fock equations through the introduction of the self‐energy operator. All relaxation and correlation effects reside in this operator, which has an energy‐dependent, nonlocal form that is systematically improvable. Perturbative arguments produce several, convenient (e.g. partial third order, outer valence Green's function, and second‐order, transition‐operator) approximations for the evaluation of valence ionization energies, electron affinities, and core ionization energies. Renormalized approaches based on Hartree–Fock or approximate Brueckner orbitals are employed when correlation effects become qualitatively important. Reference‐state total energies based on contour integrals in the complex plane and gradients of electron binding energies enable exploration of final‐state potential energy surfaces. © 2012 John Wiley & Sons, Ltd. This article is categorized under: Electronic Structure Theory > Ab Initio Electronic Structure Methods

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Brueckner orbitals, Dyson orbitals, and correlation potentials

Cited by 48 publications

References 19 publications

Photodetachment anisotropy for mixed s-p states: 8/3 and other fractions

Photodetachment anisotropy for mixed s-p states: 8/3 and other fractions

Nonperturbative time-dependent density-functional theory of ionization and harmonic generation in OCS and CS2molecules with ultrashort intense laser pulses: Intensity and orientational effects

Electron propagator theory: an approach to prediction and interpretation in quantum chemistry

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