scholarly journals Full CI Extrapolation: Application to H2O with a Double Zeta Basis Set

1986 ◽  
Vol 39 (5) ◽  
pp. 711 ◽  
Author(s):  
PD Gray ◽  
PG Burton
Keyword(s):  
Field Configuration ◽  
Basis Set ◽  
Equilibrium Geometry ◽  
Extrapolation Procedure ◽  
Consistent Field ◽  
Double Zeta ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Full Ci ◽  
Double Zeta Basis

A previously reported full CI (configuration interaction) extrapolation procedure based on multireference single and double CI, which gave excellent results for H20 at the equilibrium geometry, is extended to two other geometries for which explicit full CI results are known. The technique is shown to provide good results for cases where the SCF (self-consistent field) configuration is not strongly dominant, although degradation of performance is noticeable in these cases. The technique is also used to predict a full CI result for the 21 Al state of H20 with the double zeta basis.

Basis set convergence of atomic axial tensors obtained from self‐consistent field calculations using London atomic orbitals

1994 ◽  
Vol 100 (9) ◽  
pp. 6620-6627 ◽  
Author(s):  
Keld L. Bak ◽  
Poul Jo/rgensen ◽  
Trygve Helgaker ◽  
Kenneth Ruud ◽  
Hans Jo/rgen Aa. Jensen
Keyword(s):  
Basis Set ◽  
Set Convergence ◽  
Atomic Orbitals ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field

Universal Gaussian basis functions in relativistic quantum chemistry: atomic Dirac–Fock–Coulomb and Dirac–Fock–Breit calculations

1992 ◽  
Vol 70 (6) ◽  
pp. 1822-1826 ◽  
Author(s):  
G. L. Malli ◽  
A. B. F. Da Silva ◽  
Yasuyuki Ishikawa
Keyword(s):  
Relativistic Quantum ◽  
Basis Set ◽  
Basis Sets ◽  
Interaction Energies ◽  
Gaussian Basis Sets ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Gaussian Basis Set ◽  
Good Agreement

Matrix Dirac–Fock–Coulomb and Dirac–Fock–Breit self-consistent field calculations are performed for a number of neutral atoms. He (Z = 2) through Xe (Z = 54), using the universal Gaussian basis set (18s, 12p, 11d) reported recently by Da Silva etal. The total Dirac–Fock–Coulomb, the Dirac–Fock–Breit, and the Breit interaction energies calculated with this universal Gaussian basis set are in good agreement with the corresponding values obtained by using an extensive well-tempered Gaussian basis set for the He through Ca (Z = 20) atoms. Although this universal Gaussian basis set is inadequate for the calculation of total Dirac–Fock–Coulomb and Dirac–Fock–Breit energies for the Kr, Sr, and Xe atoms, the Breit interaction energies calculated with this basis for these three atoms are in very good agreement with the corresponding Breit interaction energies obtained by using the extensive well-tempered Gaussian basis sets. Work is in progress to generate a more extensive and energetically better universal Gaussian basis set for He through Xe for its use in non-relativistic Hartree–Fock as well as Dirac–Fock self-consistent field calculations on polyatomics involving heavy atoms.

1,n-Radical ions: the nature of the one-electron two-centre bond in cyclopropane radical cations. An abinitio SCF MO approach

1983 ◽  
Vol 61 (10) ◽  
pp. 2310-2315 ◽  
Author(s):  
Danial D. M. Wayner ◽  
Russell J. Boyd ◽  
Donald R. Arnold
Keyword(s):  
Radical Cations ◽  
Basis Set ◽  
Radical Ions ◽  
Mo Calculations ◽  
Activation Barriers ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
The One ◽  
Spin Distributions

The nature of the one-electron two-centre bond in the cyclopropane and 1,2-divinylcyclopropane radical cations is elucidated by use of abinitio self consistent field (SCF) molecular orbital (MO) calculations. The charge and spin distributions in the 90,90 and 90,0 conformations are compared at the STO-3G and 4-31G basis set levels. From energy differences between the radical cations in the 90,90 conformation and the 90,0 (transition state) conformation, the activation barriers for cis–trans isomerization in the 2A1 state of C3H6,+ and of the 1,2-divinylcyclopropane radical cation are estimated. These results are compared to previous calculations and experimental data where possible.

scholarly journals Spin State Ordering in Metal-Based Compounds Using the Localized Active Space Self-Consistent Field Method

2019 ◽  
Author(s):  
Riddhish Pandharkar ◽  
Matthew R. Hermes ◽  
Christopher J. Cramer ◽  
Laura Gagliardi
Keyword(s):  
Spin State ◽  
Computational Cost ◽  
Field Method ◽  
Basis Set ◽  
Strongly Correlated ◽  
Active Space ◽  
Embedding Theory ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field

<p>Quantitatively accurate calculations for spin state ordering in transition-metal complexes typically demand a robust multiconfigurational treatment. The poor scaling of such methods with increasing size makes them impractical for large, strongly correlated systems. Density matrix embedding theory (DMET) is a fragmentation approach that can be used to specifically address this challenge. The single-determinantal bath framework of DMET is applicable in many situations, but it has been shown to perform poorly for molecules characterized by strong correlation when a multiconfigurational self-consistent field solver is used. To ameliorate this problem, the localized active space self-consistent field (LASSCF) method was recently described. In this work, LASSCF is applied to predict spin state energetics in mono- and di-iron systems and we show that the model offers an accuracy equivalent to CASSCF but at a substantially lower computational cost. Performance as a function of basis set and active space is also examined.<br></p>

Orbital exponent optimization for molecular self-consistent-field wave functions including the polarization function

1992 ◽  
Vol 70 (2) ◽  
pp. 547-554 ◽  
Author(s):  
Kenro Hashimoto ◽  
Yoshihiro Osamura
Keyword(s):  
Wave Functions ◽  
Basis Set ◽  
Polarization Function ◽  
Orbital Exponent ◽  
Consistent Field ◽  
Energy Gradient ◽  
Double Zeta ◽  
Self Consistent Field ◽  
Polarization Functions ◽  
Field Wave

We have applied the analytical energy gradient method with respect to the orbital exponents for molecular self-consistent-field wave functions including the polarization functions. The gradients for Gaussian-type functions in Huzinaga–Dunning's double zeta basis set with and without polarization functions were compared for some hydrides of the first-row elements. The changes in the gradients caused by the polarization functions were observed. It was found that the polarization functions on hydrogen play a role in reducing the gradients produced in the absence of these functions. Although optimization of the exponents gives results depending on the molecules, the total energies as well as the dipole moments are insensitive to the exponent values. We could confirm that the exponents for Gaussian functions in the standard double zeta plus polarization basis set work adequately by coupling with the variational parameters for the simple hydrides even if they have gradients in the molecules. Keywords: orbital exponent, Gaussian-type functions, analytical energy gradient, molecular SCF wave function, polarization function.

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