scholarly journals A test of composite natural orbitals for benzene

1992 ◽  
Vol 70 (2) ◽  
pp. 532-536 ◽  
Author(s):  
Yuichi Yamamoto ◽  
Takeshi Noro ◽  
Kimio Ohno
Keyword(s):  
Excited State ◽  
Configuration Interaction ◽  
Benzene Molecule ◽  
Natural Orbital ◽  
Excitation Energies ◽  
Natural Orbitals ◽  
Experimental Values ◽  
Ci Calculations ◽  
Good Agreement

Approximate natural orbitals (NO's) of a larger system can be constructed from the NO's of smaller fragment systems. These orbitals, called composite NO's (CNO's) are expected to be useful in configuration interaction (CI) calculations. The effectiveness of these NO's is shown for the benzene molecule. This molecule is considered a combination of three ethylenes. The CI calculations were carried out for the S1 – S3 and T1 – T3 states. We take into account single and double excitations from σ and π electrons in the CI calculations. The calculated excitation energies are in good agreement with the experimental values Keywords: benzene, π–π* excited state, composite natural orbital, ionic and covalent, SDCI.

Composite natural orbitals for configuration interaction method

1988 ◽  
Vol 53 (10) ◽  
pp. 2266-2278 ◽  
Author(s):  
Yuichi Yamamoto ◽  
Takeshi Noro ◽  
Kimio Ohno
Keyword(s):  
Configuration Interaction ◽  
Ground States ◽  
New Method ◽  
Entire System ◽  
Interaction Method ◽  
Configuration Interaction Method ◽  
Excitation Energies ◽  
Natural Orbitals ◽  
Double Excitation ◽  
Ci Calculations

A new method of constructing approximate natural orbitals (NO's) is proposed. A system can usually be regarded as consisting of fragments. The approximate NO's of the entire system are constructed from the NO's of fragments in their ground states. These orbitals are expected to be useful in configuration interaction (CI) calculations of a large system where orbital truncation is necessary. The usefulness of these approximate NO's, which are called composite NO's (CNO's), is demonstrated on C4H6. This molecule may be regarded as a combination of two fragments i.e., C2H4's. Excitation energies calculated by single and double excitation CI with the truncated CNO's (14σ, 7π correlating orbitals) agree reasonably well with those calculated with a full orbital set (37σ, 12π correlating orbitals), while the truncated SCFMO's of the same size give disastrous excitation energies.

Systematic calculations of energy levels and transitions rates in Mo XXVIII

2020 ◽  
Vol 75 (8) ◽  
pp. 739-747
Author(s):  
Feng Hu ◽  
Yan Sun ◽  
Maofei Mei
Keyword(s):  
Energy Levels ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Data Sets ◽  
Electron Systems ◽  
Excitation Energies ◽  
Experimental Values ◽  
Qed Effects ◽  
Hyperfine Structures ◽  
Good Agreement

AbstractComplete and consistent atomic data, including excitation energies, lifetimes, wavelengths, hyperfine structures, Landé gJ-factors and E1, E2, M1, and M2 line strengths, oscillator strengths, transitions rates are reported for the low-lying 41 levels of Mo XXVIII, belonging to the n = 3 states (1s22s22p6)3s23p3, 3s3p4, and 3s23p23d. High-accuracy calculations have been performed as benchmarks in the request for accurate treatments of relativity, electron correlation, and quantum electrodynamic (QED) effects in multi-valence-electron systems. Comparisons are made between the present two data sets, as well as with the experimental results and the experimentally compiled energy values of the National Institute for Standards and Technology wherever available. The calculated values including core-valence correction are found to be in a good agreement with other theoretical and experimental values. The present results are accurate enough for identification and deblending of emission lines involving the n = 3 levels, and are also useful for modeling and diagnosing plasmas.

Theoretical Studies of the g Factors for Co2+ in MgO and CaO Crystals

2001 ◽  
Vol 56 (3-4) ◽  
pp. 249-252 ◽  
Author(s):  
Shao-Yi Wu ◽  
Wen-Chen Zheng
Keyword(s):  
Configuration Interaction ◽  
Optical Spectra ◽  
Theoretical Studies ◽  
Cluster Approach ◽  
Experimental Values ◽  
Good Agreement ◽  
G Factors

Abstract This paper presents a cluster approach to the calculation of the g factors for 3d7 ions in cubic oc­ tahedral crystals, in which the parameters related to the configuration interaction and the covalency reduction effects are obtained from optical spectra of the studied crystals, and so no adjustable parameters are applied. From the approach, the g factors for MgO:Co2+ and CaO:Co2+ are cal­culated. The calculated results show good agreement with the observed values. The experimental values of g 4.333 for CaO:Co2+ are also explained.

scholarly journals Eine SCF-MO-CI-Berechnung des C2 -Moleküls mit einer atomaren Basis von kontrahierten Gauß-Funktionen / An scf-mo-cl calculation of the c2 molecule using an atomic basis of contracted gaussian lobe functions

1972 ◽  
Vol 27 (7) ◽  
pp. 1031-1041 ◽  
Author(s):  
J Barsuhn
Keyword(s):  
Experimental Data ◽  
Basis Set ◽  
Basis Sets ◽  
Excitation Energies ◽  
Experimental Values ◽  
Extensive Experimental Data ◽  
The Relationship ◽  
Ci Calculations ◽  
State Configuration ◽  
Slater Basis

Abstract The C2-molecule seems to be a very useful object for the purpose of comparing different quantum chemical calculations because of the extensive experimental data available for this molecule. In the present treatment a basis set consisting of 25 primitive Gaussian lobe functions which have been contracted into 4 s-groups and 2X3 p-groups has been used. SCF orbitals obtained for the ground state configuration 1 πu4 have been employed in two CI-calculations at R-values in the vicinity of the equilibrium internuclear distance. The calculation involving only virtual a-orbitals agrees qualitatively with the experimental data for the three known Rydberg states. The most extensive Cl-treatment employed overestimates the excitation energies to the higher states by up to 1.7 eV; the relationship between the theoretically calculated transition energies and the corresponding experimental values is approximately linear, however. The results are compared with previous extensive CI-calculations of FOUGERE and NESBET who used two different 2-zeta Slater basis sets

scholarly journals Multiconfiguration Dirac-Hartree-Fock calculations of Landé g-factors for ions of astrophysical interest: B II, C I−IV, Al I−II, Si I−IV, P II, S II, Cl III, Ar IV, Ca I, Ti II, Zr III, and Sn II

2020 ◽  
Vol 639 ◽  
pp. A25 ◽  
Author(s):  
W. Li ◽  
P. Rynkun ◽  
L. Radžiūtė ◽  
G. Gaigalas ◽  
B. Atalay ◽  
...  
Keyword(s):  
General Purpose ◽  
Wave Functions ◽  
Excitation Energies ◽  
Hartree Fock ◽  
Relativistic Configuration ◽  
Experimental Values ◽  
Relativistic Configuration Interaction ◽  
Relative Differences ◽  
Average Uncertainty ◽  
Good Agreement

Aims. The Landé g-factor is an important parameter in astrophysical spectropolarimetry, used to characterize the response of a line to a given value of the magnetic field. The purpose of this paper is to present accurate Landé g-factors for states in B II, C I−IV, Al I−II, Si I−IV, P II, S II, Cl III, Ar IV, Ca I, Ti II, Zr III, and Sn II. Methods. The multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction methods, which are implemented in the general-purpose relativistic atomic structure package GRASP2K, are employed in the present work to compute the Landé g-factors for states in B II, C I−IV, Al I−II, Si I−IV, P II, S II, Cl III, Ar IV, Ca I, Ti II, Zr III, and Sn II. The accuracy of the wave functions for the states, and thus the accuracy of the resulting Landé g-factors, is evaluated by comparing the computed excitation energies and energy separations with the National Institute of Standards and Technology (NIST) recommended data. Results. All excitation energies are in very good agreement with the NIST values except for Ti II, which has an average difference of 1.06%. The average uncertainty of the energy separations is well below 1% except for the even states of Al I; odd states of Si I, Ca I, Ti II, Zr III; and even states of Sn II for which the relative differences range between 1% and 2%. Comparisons of the computed Landé g-factors are made with available NIST data and experimental values. Analysing the LS-composition of the wave functions, we quantify the departures from LS-coupling and summarize the states for which there is a difference of more than 10% between the computed Landé g-factor and the Landé g-factor in pure LS-coupling. Finally, we compare the computed Landé g-factors with values from the Kurucz database.

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