[en] The self-consistent FFS theory versus the HF method with effective forces is reviewed

[en] Published in summary form only

No abstract available

[en] We present here an attempt to include the effects of neighboring atoms within the framework of the self-consistent average atom procedure. Multiple scattering formalism developed for the study of liquid metals and amorphous materials is used to describe the effect of the adjacent scatterers in dense plasma problems. The influence of a single nearest neighbor on the density of states of the 2p resonance in highly compressed aluminium is investigated. The multiple scattering formalism is incorporated into a full self-consistent average atom calculation, this procedure is discussed here in detail. The pressure using this procedure is compared to that obtained using the LMTO method

[en] The general applicability of molecular methods for studying hyperfine pressure shifts (HPS) in a hydrogen atom caused by Ar and He noble-gas buffers has been tested thoroughly by carrying out extensive multiconfigurational self-consistent-field (MCSCF) and single-configuration self-consistent-field (SCF) calculations on ArH and HeH diatomic systems. Calculations show that for a He atom, a light noble-gas buffer, single-configuration SCF molecular wave functions are sufficiently good in reproducing the HPS result quantitatively, although qualitatively the weak, long-range polarization features are not described. However, for a heavier noble-gas buffer, such as the Ar atom, the long-range polarization effects are the strong and dominant features in the ArH binary interaction. Because of a lack of a sufficient number of proper functions for describing the long-range polarization features, the single-configuration SCF molecular wave functions do not reproduce the long-range polarization effects adequately. For ArH, therefore, MCSCF molecular wave functions, constructed with a choice of configurations which describe the dominant polarizations, are employed to reproduce the HPS result quantitatively and the long-range features qualitatively. HPS results computed by using MCSCF molecular wave functions are in excellent agreement with the experimental result

No abstract available

[en] The 0s orbitals, i.e., functions of the form [exp(-ar)-exp(-br)]/r, appear in the iterative solution of the Hartree--Fock equations. The inclusion of these functions in the basis set for the standard SCF calculation for helium is shown to give much better values for the SCF energy than those obtained by using the 1s functions alone, especially in smaller basis sets. This result is rather contradictory to a previous work of Zung and Parr. Using a five term basis set we have obtained the SCF energy of the He atom to be equal to -2.861 679 995 612 a.u. Our results indicate that the disagreement between the Roothaan--Soukup and Gazquez--Silverstone ''SCF limits'' for the He atom should be resolved in favor of the latter, which is identical with our result to all digits quoted. A routine use of the 0s functions in SCF calculations for atoms and molecules is advocated

[en] Recently, an improved approximate self-consistent dual topological unitarization technique has been developed, in which the effect of planar ''sea''-quark loops is taken into account from the beginning. This is applied to qqq and qqantiqantiq hadrons with q=u, d, s, and good agreement is obtained with experiment. In particular, we predict 2^- and 3⁺ Λantip states which could be identified with recently observed broad resonances of mass 2.20 and 2.33 GeV

[en] Highlights: • SCF acceleration techniques based on DIIS were implemented into the GHF framework. • Five convergence techniques were assessed for spin-dependent relativistic cases. • A combination of DIIS and EDIIS stably and efficiently converges GHF. This Letter assesses the self-consistent field (SCF) convergence behavior in the generalized Hartree–Fock (GHF) method. Four acceleration algorithms were implemented for efficient SCF convergence in the GHF method: the damping algorithm, the conventional direct inversion in the iterative subspace (DIIS), the energy-DIIS (EDIIS), and a combination of DIIS and EDIIS. Four different systems with varying complexity were used to investigate the SCF convergence using these algorithms, ranging from atomic systems to metal complexes. The numerical assessments demonstrated the effectiveness of a combination of DIIS and EDIIS for GHF calculations in comparison with the other discussed algorithms.

[en] The charge transfer (CT) interaction, the most time-consuming term in the general effective fragment potential method, is made much more computationally efficient. This is accomplished by the projection of the quasiatomic minimal-basis-set orbitals (QUAMBOs) as the atomic basis onto the self-consistent field virtual molecular orbital (MO) space to select a subspace of the full virtual space called the valence virtual space. The diagonalization of the Fock matrix in terms of QUAMBOs recovers the canonical occupied orbitals and, more importantly, gives rise to the valence virtual orbitals (VVOs). The CT energies obtained using VVOs are generally as accurate as those obtained with the full virtual space canonical MOs because the QUAMBOs span the valence part of the virtual space, which can generally be regarded as “chemically important.” The number of QUAMBOs is the same as the number of minimal-basis MOs of a molecule. Therefore, the number of VVOs is significantly smaller than the number of canonical virtual MOs, especially for large atomic basis sets. This leads to a dramatic decrease in the computational cost