Dynamical Electron Correlation Within Hartree-Fock Limitation

10.26434/chemrxiv.5357404 ◽

2017 ◽

Author(s):

Arijit Bag

Keyword(s):

Small Molecules ◽

Electron Correlation ◽

Present Method ◽

Correlation Energy ◽

Electronic Structure Theory ◽

Structure Theory ◽

Coupled Cluster ◽

Energy Correlation ◽

Good Tool ◽

Hartree Fock

Aim: Calculation of dynamical electron correlation energy within Hartree Fock formalism to achieve post Hartree Fock accuracy. Achievement: Using intermediate Hamiltonian technique and perturbation methodology we can construct a weave equation which on projection gives very simple equation for correlation energy. Correlation energy only depends on the amount of perturbation. This method is applied for few small molecules. It is found that this method produces very accurate results which is comparable to CCSD method. Conclusion: The present method which is termed as Extended Hartree Fock (EHF) method is proved to be a very good tool for electronic structure theory as its computational requirement is equivalent to HF method but its accuracy is comparable to Coupled Cluster based methods.

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Electronic Structure Theory for X-Ray Absorption and Photoemission Spectroscopy

Springer Proceedings in Physics - Magnetism and Accelerator-Based Light Sources ◽

10.1007/978-3-030-64623-3_3 ◽

2021 ◽

pp. 63-81

Author(s):

Peter Krüger

Keyword(s):

Electronic Structure ◽

Electron Correlation ◽

Density Functional ◽

Electronic Structure Theory ◽

Structure Theory ◽

Photoemission Spectroscopy ◽

Functional Theory ◽

X Ray ◽

Hartree Fock ◽

X Ray Absorption

AbstractThe principles of X-ray absorption and photoemission spectroscopy calculations are introduced and the basics of electronic structure theory, including the Hartree–Fock approximation, density functional theory, its time-dependent version and quasiparticle theory are reviewed on an elementary level. Emphasis is put on polarization effects and the role played by electron correlation.

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Restricted Hartree Fock using complex-valued orbitals: A long-known but neglected tool in electronic structure theory

The Journal of Chemical Physics ◽

10.1063/1.4905120 ◽

2015 ◽

Vol 142 (2) ◽

pp. 024104 ◽

Cited By ~ 19

Author(s):

David W. Small ◽

Eric J. Sundstrom ◽

Martin Head-Gordon

Keyword(s):

Electronic Structure ◽

Electronic Structure Theory ◽

Structure Theory ◽

Hartree Fock ◽

Complex Valued

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Coupled-cluster approach in electronic structure theory of molecules

Physics Reports ◽

10.1016/0370-1573(82)90168-5 ◽

1982 ◽

Vol 90 (3) ◽

pp. 159-202 ◽

Cited By ~ 48

Author(s):

V. Kvasnička ◽

V. Laurinc ◽

S. Biskupič

Keyword(s):

Electronic Structure ◽

Electronic Structure Theory ◽

Structure Theory ◽

Coupled Cluster ◽

Cluster Approach

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Efficient electronic structure theory via hierarchical scale-adaptive coupled-cluster formalism: I. Theory and computational complexity analysis

Molecular Physics ◽

10.1080/00268976.2017.1367856 ◽

2017 ◽

Vol 116 (5-6) ◽

pp. 588-601

Author(s):

Dmitry I. Lyakh

Keyword(s):

Electronic Structure ◽

Computational Complexity ◽

Complexity Analysis ◽

Electronic Structure Theory ◽

Structure Theory ◽

Coupled Cluster ◽

Hierarchical Scale

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An approximate ab initio method based on the DIM model

Canadian Journal of Chemistry ◽

10.1139/v00-143 ◽

2000 ◽

Vol 78 (12) ◽

pp. 1575-1586 ◽

Cited By ~ 4

Author(s):

John M Cullen

Keyword(s):

Ab Initio ◽

Excited States ◽

Electron Correlation ◽

Correlation Energy ◽

Basis Sets ◽

Ab Initio Method ◽

First Order ◽

Hartree Fock ◽

Modified Method ◽

Electron Correlation Energy

Using a second quantized formulation, an approximate diatomics in molecules (DIM) theory is presented in which all three- and four-centered electronic integrals are neglected. To ameliorate the effects of this approximation, the DIM one electron operator is constructed so that the true ab initio first-order density matrix and total energy are reproduced at the HartreeFock level. The resulting model was extensively tested for a variety of basis sets for its capability of capturing both the dynamic and nondynamic components of the electron correlation energy as well as the energies of excited electronic states. A modified method in which the DIM one-electron operator is formed from the initial extended Hückel guess of the HartreeFock orbitals was also found to produce excellent results.Key words: DIM, electron correlation energy, excited states, semiempirical.

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The Usefulness of Exponential Wave Function Expansions Employing One- and Two-Body Cluster Operators in Electronic Structure Theory: The Extended and Generalized Coupled-Cluster Methods

Advances in Quantum Chemistry ◽

10.1016/s0065-3276(06)51001-9 ◽

2006 ◽

pp. 1-57 ◽

Cited By ~ 35

Author(s):

Peng-Dong Fan ◽

Piotr Piecuch

Keyword(s):

Wave Function ◽

Electronic Structure ◽

Electronic Structure Theory ◽

Structure Theory ◽

Coupled Cluster ◽

Coupled Cluster Methods ◽

Cluster Methods

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Energies and structures in biradical chemistry from the parametric two-electron reduced-density matrix method: applications to the benzene and cyclobutadiene biradicals

Physical Chemistry Chemical Physics ◽

10.1039/c5cp01310k ◽

2015 ◽

Vol 17 (19) ◽

pp. 12521-12529 ◽

Cited By ~ 3

Author(s):

Alison L. McManus ◽

Erik P. Hoy ◽

David A. Mazziotti

Keyword(s):

Electronic Structure ◽

Density Matrix ◽

Electron Correlation ◽

Matrix Method ◽

Electronic Structure Theory ◽

Reduced Density Matrix ◽

Structure Theory ◽

Reference Methods ◽

Reduced Density

The treatment of biradical chemistry presents a challenge for electronic structure theory, especially single-reference methods, as it requires the description of varying degrees and kinds of electron correlation.

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