Comment on "Theoretical calculations on ions and radicals. I. A restricted Hartree-Fock perturbation method for the calculation of spin densities"

1967 ◽  
Vol 71 (9) ◽  
pp. 3099-3100 ◽  
Author(s):  
James R. Bolton
Keyword(s):  
Perturbation Method ◽  
Theoretical Calculations ◽  
Hartree Fock ◽  
Spin Densities

Use of a Lowest Intensity 241Am Compton Spectrometer for the Measurement of Directional Compton Profiles of ZnSe

2006 ◽  
Vol 61 (7-8) ◽  
pp. 364-370 ◽  
Author(s):  
Babu Lal Ahuja ◽  
Narayan Lal Heda
Keyword(s):  
Bond Length ◽  
Theoretical Calculations ◽  
The Other ◽  
Energy Bands ◽  
Electron Momentum ◽  
Atomic Orbitals ◽  
Hartree Fock ◽  
Self Consistent ◽  
Scattering Technique ◽  
Small Disc

In this paper we report on electron momentum densities in ZnSe using Compton scattering technique. For the directional measurements we have employed a newly developed 100 mCi 241Am Compton spectrometer which is based on a small disc source with shortest geometry. For the theoretical calculations we have employed a self-consistent Hartree-Fock linear combination of atomic orbitals (HF-LCAO) approach. It is seen that the anisotropy in the measured Compton profiles is well reproduced by our HF-LCAOcalculation and the other available pseudopotential data. The anisotropy in the Compton profiles is explained in terms of energy bands and bond length. - PACS numbers: 13.60.Fz, 78.70. Ck, 78.70.-g

scholarly journals Vibrationally and Spin-Orbit-Resolved Inner-Shell X-ray Absorption Spectroscopy of the NH+ Molecular Ion: Measurements and ab Initio Calculations

Atoms ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 67
Author(s):  
Stéphane Carniato ◽  
Jean-Marc Bizau ◽  
Denis Cubaynes ◽  
Eugene T. Kennedy ◽  
Ségolène Guilbaud ◽  
...  
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Theoretical Calculations ◽  
High Sensitivity ◽  
Open Shell ◽  
Field Configuration ◽  
High Spectral Resolution ◽  
Spin Orbit ◽  
Molecular Ion ◽  
Hartree Fock

This article presents N2+ fragment yields following nitrogen K-shell photo-absorption in the NH+ molecular ion measured at the SOLEIL synchrotron radiation facility in the photon energy region 390–450 eV. The combination of the high sensitivity of the merged-beam, multi-analysis ion apparatus (MAIA) with the high spectral resolution of the PLEIADES beamline helped to resolve experimentally vibrational structures of highly excited [N1s−1H]*+ electronic states with closed or open-shell configurations. The assignment of the observed spectral features was achieved with the help of density functional theory (DFT) and post-Hartree Fock Multiconfiguration Self-Consistent-Field/Configuration Interaction (MCSCF/CI) ab-initio theoretical calculations of the N1s core-to-valence and core-to-Rydberg excitations, including vibrational dynamics. New resonances were identified compared to previous work, owing to detailed molecular modeling of the vibrational, spin-orbit coupling and metastable state effects on the spectra. The latter are evidenced by spectral contributions from the 4Σ− electronic state which lies 0.07 eV above the NH+2Π ground state.

Accuracy Assessment of the ROHF-CCSD(T) Calculationsof Dipole Moments of Small Radicals

1998 ◽  
Vol 63 (9) ◽  
pp. 1409-1430 ◽  
Author(s):  
Miroslav Urban ◽  
Pavel Neogrády ◽  
Juraj Raab ◽  
Geerd H. F. Diercksen
Keyword(s):  
Large Deviation ◽  
Theoretical Calculations ◽  
Dipole Moments ◽  
Accuracy Assessment ◽  
Open Shell ◽  
Basis Set ◽  
Coupled Cluster ◽  
Hartree Fock ◽  
Experimental Values

Dipole moments of a series of radicals, OH, NO, NS, SF, SO, PO, ClO, CN, LiO, NO2, and ClO2 were calculated by the Coupled Cluster CCSD(T) method with the single determinant restricted open shell Hartree-Fock (ROHF) reference. For all molecules theoretical dipole moments were carefully compared to experimental values. The size and the quality of the basis set were systematically improved. Spin adaptation in the ROHF-CCSD(T) method, largest single and double excitation amplitudes and the T1 diagnostics were considered as indicators in the quality assessment of calculated dipole moments. For most molecules the accuracy within 0.01-0.03 D was readily obtained. For ClO and CN the spin adaptation was necessary - its contribution was as large as 0.03-0.045 D. Large deviation from experiment is observed for OH in its A2Σ+ excited state (0.135 D) and especially for LiO in its 2Π ground state (0.22 D). No indication of the failure of theoretical calculations was found which leads to the conclusion that, even if there is still a space for the improvement of theoretical calculations, experimental values should be reconsidered.

Theoreticalversusexperimental geometries in S-bridged manganese carbonyl complexes

2003 ◽  
Vol 36 (4) ◽  
pp. 1050-1055 ◽  
Author(s):  
Juan F. Van der Maelen Uría ◽  
Javier Ruiz ◽  
Santiago García-Granda
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Basis Sets ◽  
Medium Size ◽  
Carbonyl Complexes ◽  
X Ray Diffraction ◽  
Bond Lengths ◽  
Hartree Fock ◽  
Experimental Geometry ◽  
Manganese Carbonyl

The experimental geometry obtained from single-crystal X-ray diffraction for a number of binuclear S-bridged manganese complexes is compared with the results of theoretical calculations made at theab initiolevel by using Hartree–Fock and density functional theory methods with medium-size and large basis sets. The optimized geometries obtained were somewhat relaxed when compared with the experimental ones, with very similar bond and torsion angles but longer bond lengths. The mean square deviation for bond lengths (angles) was found to be between 0.046 Å (1.1°) and 0.004 Å (0.7°) depending on the theoretical model used.

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