Open-shell localized Hartree–Fock method based on the generalized adiabatic connection Kohn–Sham formalism for a self-consistent treatment of excited states

2005 ◽  
Vol 122 (24) ◽  
pp. 244102 ◽  
Author(s):  
Vincenzo Vitale ◽  
Fabio Della Sala ◽  
Andreas Görling
Keyword(s):  
Excited States ◽  
Open Shell ◽  
Hartree Fock ◽  
Self Consistent ◽  
Consistent Treatment

Self-Consistent Treatment of the Pauli Operator in the Brueckner-Hartree-Fock Approach

1973 ◽  
Vol 8 (1) ◽  
pp. 129-134 ◽  
Author(s):  
Ram K. Tripathi ◽  
Amand Faessler ◽  
Alan D. MacKellar
Keyword(s):  
Pauli Operator ◽  
Hartree Fock ◽  
Self Consistent ◽  
Consistent Treatment

Self-consistent Field Orbital Methods

2020 ◽  
pp. 128-149
Author(s):  
Jochen Autschbach
Keyword(s):  
Density Functional ◽  
Slater Determinant ◽  
Closed Shell ◽  
Open Shell ◽  
Initial Guess ◽  
Hartree Fock ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Definition Of

This chapter discusses the concepts underlying the Hartree-Fock (HF) electronic structure method. First, it is shown how the energy expectation value is calculated for a Slater determinant (SD) wavefunction in the case of orthonormal orbitals. This leads to the definition of the electron repulsion integrals (ERIs). Next, the energy is minimized subject to the orthonormality constraints. This leads to the HF equation for the orbitals. The HF orbital energies are Langrange multipliers representing the constraints. An unknown set of orbitals can be determined from an initial guess via a self-consistent field (SCF) cycle. The HF scheme is discussed for closed-shell versus open shell systems, leading to the distinction between spin restricted and unrestricted HF (RHF, UHF). Kohn-Sham density functional theory (DFT) is introduced and its approximate version is placed in the context of ab-initio versus semi-empirical quantum chemistry methods.

scholarly journals Excited States of Crystalline Point Defects with Multireference Density Matrix Embedding Theory

2021 ◽  
Author(s):  
Abhishek Mitra ◽  
Hung Pham ◽  
Riddhish Pandharkar ◽  
Matthew Hermes ◽  
Laura Gagliardi
Keyword(s):  
Density Matrix ◽  
Excited States ◽  
Open Shell ◽  
Electronic Excitations ◽  
Complete Active Space ◽  
Hartree Fock ◽  
Embedding Theory ◽  
Consistent Field ◽  
Matrix Embedding ◽  
Self Consistent Field

Accurate and affordable methods to characterize the electronic structure of solids are important for targeted materials design. Embedding-based methods provide an appealing balance in the trade-off between cost and accuracy - particularly when studying localized phenomena. Here, we use the density matrix embedding theory (DMET) algorithm to study the electronic excitations in solid-state defects with a restricted open-shell Hartree--Fock (ROHF) bath and multireference impurity solvers, specifically, complete active space self-consistent field (CASSCF) and n-electron valence state second-order perturbation theory (NEVPT2). We apply the method to investigate an oxygen vacancy (OV) on a MgO(100) surface and find absolute deviations within 0.05 eV between DMET using the CASSCF/NEVPT2 solver, denoted as CAS-DMET/NEVPT2-DMET, and the non-embedded CASSCF/NEVPT2 approach. Next, we establish the practicality of DMET by extending it to larger supercells for the OV defect and a neutral silicon-vacancy in diamond where the use of non-embedded CASSCF/NEVPT2 is extremely expensive.

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