AB-INITIO CALCULATION OF CORRELATION EFFECTS IN METALLIC LITHIUM

1993 ◽  
Vol 07 (01n03) ◽  
pp. 258-261
Author(s):  
ANDREA HEILINGBRUNNER ◽  
GERNOT STOLLHOFF
Keyword(s):  
Binding Energy ◽  
Bulk Modulus ◽  
Ab Initio ◽  
Ground State ◽  
Ab Initio Calculation ◽  
Correlation Effects ◽  
Charge Fluctuations ◽  
Hartree Fock ◽  
Metallic Lithium ◽  
Local Operators

We present an ab initio calculation of the correlation effects in metallic lithium. The calculation is carried out based on the use of local operators (Local Ansatz), where correlations are included as corrections to the Hartree-Fock (HF) ground state. We investigate the strength of longer range correlations and their dependance on distance, which allows us to discuss complementary findings to LDA results. The correlation contributions to the binding energy are extracted. The missing longer range correlations can be estimated. Effects of correlations on the bulk modulus, lattice constant and charge fluctuations are analysed. The structural phases of Li with bcc- and fcc-symmetry are compared.

scholarly journals THE METHOD OF INCREMENTS — A WAVEFUNCTION-BASED AB-INITIO CORRELATION METHOD FOR SOLIDS

2007 ◽  
Vol 21 (13n14) ◽  
pp. 2204-2214 ◽  
Author(s):  
BEATE PAULUS
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Ground State ◽  
Infinite System ◽  
Correlation Energy ◽  
Correlation Method ◽  
Many Body ◽  
Hartree Fock ◽  
The Many ◽  
Good Agreement

The method of increments is a wavefunction-based ab initio correlation method for solids, which explicitly calculates the many-body wavefunction of the system. After a Hartree-Fock treatment of the infinite system the correlation energy of the solid is expanded in terms of localised orbitals or of a group of localised orbitals. The method of increments has been applied to a great variety of materials with a band gap, but in this paper the extension to metals is described. The application to solid mercury is presented, where we achieve very good agreement of the calculated ground-state properties with the experimental data.

Ab initio Calculation of the Dipole Moment Function of the OH Radical Ground State

2018 ◽  
Vol 12 (6) ◽  
pp. 970-976
Author(s):  
S. O. Adamson ◽  
D. D. Kharlampidi ◽  
G. V. Golubkov ◽  
M. I. Manzhelii ◽  
S. S. Nabiev ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Ab Initio ◽  
Ground State ◽  
Ab Initio Calculation ◽  
Moment Function ◽  
Oh Radical

Ab initio Correlation Effects in Density Functional Theories: An Electron-Distribution-Based Study for Neon

2005 ◽  
Vol 70 (8) ◽  
pp. 1157-1176 ◽  
Author(s):  
Karol Jankowski ◽  
Ireneusz Grabowski ◽  
Krzysztof Nowakowski ◽  
Jan Wasilewski
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Physical Nature ◽  
Correlation Effects ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Hartree Fock ◽  
Brueckner Orbitals ◽  
Local Gradient ◽  
The Impact

We have briefly reviewed the idea of studies aiming at such a bridging of the methodological gap between ab initio methods (or wave function theory (WFT)) and density functional theory (DFT) that would afford carrying over results concerning details of the structure of correlation effects from one method to the other. Special attention is paid to the problem of coverage of the WFT correlation effects by the exchange-correlation functionals of DFT. A short survey of the concept of supplementing energy-based investigations in this field by electron-density-based studies is given and illustrated by results for the Ne atom. DFT densities are generated for representatives of all four generations of presently used exchange-correlation functionals, including the recently developed orbital-dependent one. These densities are compared with WFT densities calculated at the MP2, MP3, and Brueckner determinant levels. It is found that the exchange-only parts of the local, gradient-corrected, and hybrid functionals account for the bulk of WFT correlation effects. The impact of the associated correlation functionals is very small and their physical nature is not quite clear. The situation is different for the orbital-dependent functional for which the exchange-only functional provides an almost exact description of the Hartree-Fock density. Here, the correlation effects are entirely represented by the correlation functional. Attention is also paid to the suitability of Kohn-Sham orbitals for the description of WFT correlation effects and to their presumptive similarity with Brueckner orbitals.

Simplified Non-Empirical Unrestricted Hartree-Fock Approximation (SUHF) for the Calculation of Electronic Ground State Properties of Molecules with Closed and Open Valence Shells. I. Method

1993 ◽  
Vol 48 (7) ◽  
pp. 829-833
Author(s):  
Wolfhard Koch
Keyword(s):  
Electron Correlation ◽  
Ground State ◽  
Atomic Orbital ◽  
Closed Shell ◽  
Open Shell ◽  
Polyatomic Molecules ◽  
Correlation Effects ◽  
Hartree Fock ◽  
Electron Correlation Effects ◽  
Electronic Ground

Abstract Focusing on relative stabilities of electronic states with different spin multiplicities of polyatomic molecules, a simplified unrestricted Hartree-Fock (SUHF) procedure is described. Using different orbitals for different spins (DODS), electron correlation effects of both closed-shell and open-shell systems are expected to be taken into account in the simplest way. While working within a symmetrically orthogonalized (Löwdin) basis we make use of the NDDO approximation (neglect of diatomic differential overlap) concerning the evaluation of electron repulsion and nuclear attraction integrals. Originally, a locally orthogonalized all-electron atomic orbital set of Slater type is considered. The approximation method is completely non-empirical. Rotational invariance is fully retained.

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