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Electron Pair Approximation

In the language of configuration interaction, one uses the wave function [Pg.85]

For technical details of calculations such as the use of pair natural [Pg.86]


Coupled—Pair Functional (ACPF) and Coupled Electron Pair Approximation (CEPA). The simplest form of CEPA, CEPA-0, is also known as Linear Coupled Cluster Doubles (LCCD). [Pg.139]

Coupled Electron Pair Approximation Botschwina and Sebald, Ref. 98. [Pg.38]

Hartree-Fock with Proper Dissociation Internally Consistent Self Consistent Orbitals Independent Electron Pair Approximation Intermediate Neglect of Differential Overlap Intermediate Retention of Differential Overlap Iterative Natural Orbital Ionization Potential... [Pg.235]

The relationship between the coupled-electron pair approximation (c.e.p.a.) and the many-body perturbation theory has been discussed in detail by Ahl-richs.149 All of the methods denoted by c.e.p.a. (x) (x=0, 1, 2, 3) may be related to the summation of certain classes of diagrams in the many-body perturbation theory to infinite order. For example, c.e.p.a. (0), which is Cizek s linear approximation or Hurley s c.p.a. (0) ansatz150 is equivalent to the summation of all double-excitation linked diagrams in the perturbation series. This is also denoted d.e.m.b.p.t. (double excitation many-body perturbation theory) by some workers.151 168... [Pg.32]

Electron Pair Approximation with Pair Natural Orbitals) Calculations of Molecular Systems. I. Outline of the Method for Closed-Shell States. [Pg.289]

Besides the mentioned aperiodicity problem the treatment of correlation in the ground state of a polymer presents the most formidable problem. If one has a polymer with completely filled valence and conduction bands, one can Fourier transform the delocalized Bloch orbitals into localized Wannier functions and use these (instead of the MO-s of the polymer units) for a quantum chemical treatment of the short range correlation in a subunit taking only excitations in the subunit or between the reference unit and a few neighbouring units. With the aid of the Wannier functions then one can perform a Moeller-Plesset perturbation theory (PX), or for instance, a coupled electron pair approximation (CEPA) (1 ), or a coupled cluster expansion (19) calculation. The long range correlation then can be approximated with the help of the already mentioned electronic polaron model (11). [Pg.78]

CEPA Coupled Electron Pair Approximation for including dynamic correlations. [Pg.393]

The multi-reference coupled electron pair approximation (MRCEPA) has a long pedigree as one of the more rigorous quantum chemical procedures. A recent development, the state specific version (SS-MRCEPA) has been... [Pg.95]

This defines an independent electron pair approximation in terms of extremal pairs, which can be regarded as a generalization of the independent electron pair approximation (IEPA) [4, 8] in terms of pairs (ij) constructed form (preferably) localized orbitals. As in the discussion in Paper I for MP2 [5], one can show that the extremal pairs defined in this section are related to approximate natural geminals corresponding to the coupled-cluster wave function. [Pg.28]

Computation of Excited State Potential Energy Surfaces via Linear Response Theories Based on State Specific Multi-Reference Coupled Electron-Pair Approximation Like Methods (S. Chattopadhyay, D. Pahari, U. Mahapatra D. Mukherjee)... [Pg.334]


See other pages where Electron Pair Approximation is mentioned: [Pg.310]    [Pg.88]    [Pg.88]    [Pg.161]    [Pg.290]    [Pg.340]    [Pg.150]    [Pg.97]    [Pg.97]    [Pg.137]    [Pg.140]    [Pg.316]    [Pg.95]    [Pg.8]    [Pg.127]    [Pg.129]    [Pg.141]    [Pg.193]    [Pg.274]    [Pg.85]    [Pg.97]    [Pg.8]    [Pg.9]    [Pg.394]    [Pg.77]    [Pg.150]    [Pg.150]    [Pg.81]    [Pg.15]    [Pg.304]    [Pg.168]    [Pg.252]    [Pg.275]   


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Electron-pairing approximation

Pair approximation

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