Numerical method for the open-shell restricted hartree-fock density-matrix direct calculation

1985 ◽  
Vol 27 (6) ◽  
pp. 653-664 ◽  
Author(s):  
M. M. Mestechkin
Keyword(s):  
Density Matrix ◽  
Numerical Method ◽  
Direct Calculation ◽  
Open Shell ◽  
Hartree Fock

Hartree-fock density matrix equation: Open-shell systems

2009 ◽  
Vol 18 (S14) ◽  
pp. 161-165
Author(s):  
C. Frishberg ◽  
L. Cohen ◽  
P. Blumenau
Keyword(s):  
Density Matrix ◽  
Matrix Equation ◽  
Open Shell ◽  
Hartree Fock ◽  
Density Matrix Equation

THEORY OF ORBITAL SPLITTING IN METALS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 255-257 ◽  
Author(s):  
LUKAS SEVERIN ◽  
M. S. S. BROOKS ◽  
BÖRJE JOHANSSON
Keyword(s):  
Density Matrix ◽  
Ab Initio ◽  
Spin Density ◽  
Open Shell ◽  
Spin Density Matrix ◽  
Hartree Fock ◽  
Local Spin ◽  
Scaling Procedure ◽  
Good Agreement

A theory for orbital splitting is derived from a statistical Hartree-Fock (HF) treatment of open shell interactions. In a scaling procedure, where the HF spinpolarization matrix is replaced by the corresponding local spin density matrix, an expression for the orbital splitting is derived which is well suited for implementation in the standard ab initio calculational scheme. Results for Co metal as well as for the itinerant 5f ferromagnet US is presented, which are in good agreement with experiment.

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.

Analytic energy gradients for open-shell coupled-cluster singles and doubles (CCSD) calculations using restricted open-shell Hartree—Fock (ROHF) reference functions

1991 ◽  
Vol 182 (3-4) ◽  
pp. 207-215 ◽  
Author(s):  
Jürgen Gauss ◽  
Walter J. Lauderdale ◽  
John F. Stanton ◽  
John D. Watts ◽  
Rodney J. Bartlett
Keyword(s):  
Open Shell ◽  
Coupled Cluster ◽  
Hartree Fock ◽  
Reference Functions

MO-Theoretical Studies on a Model Complex for Deoxymyoglobin

1998 ◽  
Vol 53 (9) ◽  
pp. 755-765
Author(s):  
Christian Kollma ◽  
Sighart F. Fischer ◽  
Michael C. Böhm
Keyword(s):  
High Spin ◽  
Ground State ◽  
High Spin State ◽  
Open Shell ◽  
Spin States ◽  
Hartree Fock ◽  
Intermediate Spin ◽  
Model Complex ◽  
Out Of Plane ◽  
Overlap Method

AbstractThe origin of the displacement of the Fe atom in deoxymyoglobin with respect to the porphyrin plane in the high-spin state is examined by a qualitative molecular orbital (MO) analysis on the extended Hückel level. We find that attachment of a fifth ligand (imidazole in our model complex) to Fe(II)porphyrin favors the out-of-plane shift due to a strengthening of the bonding interaction between Fe and the nitrogen of the imidazole ligand. This results in a high-spin (5 = 2) ground state with Fe shifted out-of-plane for the five-coordinate complex instead of an intermediate spin ground state (5 = 1) with Fe lying in the plane for four-coordinate Fe(II)porphyrin. The relative energies of the different spin states as a function of the distance between Fe and the porphyrin plane are evaluated using an ROHF (restricted open shell Hartree-Fock) version of an INDO (intermediate neglect of differential overlap) method. We observe a level crossing between high-spin and intermediate spin states whereas the low-spin (5 = 0) state remains always higher in energy.

scholarly journals Evaluation of the one electron expectation values for different wave function of Be atom

2007 ◽  
Vol 4 (3) ◽  
pp. 393-396
Author(s):  
Baghdad Science Journal
Keyword(s):  
Wave Function ◽  
Slater Determinant ◽  
Open Shell ◽  
Expectation Values ◽  
Electronic Density ◽  
Expectation Value ◽  
Hartree Fock ◽  
Shell System ◽  
Electronic Wave Function ◽  
The One

The aim of this work is to evaluate the one- electron expectation value from the radial electronic density function D(r1) for different wave function for the 2S state of Be atom . The wave function used were published in 1960,1974and 1993, respectavily. Using Hartree-Fock wave function as a Slater determinant has used the partitioning technique for the analysis open shell system of Be (1s22s2) state, the analyze Be atom for six-pairs electronic wave function , tow of these are for intra-shells (K,L) and the rest for inter-shells(KL) . The results are obtained numerically by using computer programs (Mathcad).

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