Ground and Excited Electronic Energy Surfaces of the MnS4 Cluster in ZnS:Mn2+

1986 ◽  
Vol 89 ◽  
Author(s):  
J. W. Richardson ◽  
G. J. H. Janssen
Keyword(s):  
Stokes Shift ◽  
Electronic Energy ◽  
Correlation Effects ◽  
Excitation Energies ◽  
Self Consistent Field ◽  
Jahn Teller ◽  
Electron Correlation Effects ◽  
Stabilization Energies ◽  
Energy Surfaces ◽  
Quartet Level

AbstractGaussian-based Self Consistent Field (SCF) MOs are obtained at various nuclear geometries for the MnS4 cluster in the external potential of cubic ZnS. Electronic relaxation and d-shell electron correlation effects are then included. For Td symmetry, quartet d-d excitation energies calculated as functions of R(Mn-S) qualitatively resemble the simple CF diagram. While separations between successive quartet levels agree closely with experiment, the threshold is about 0.5 eV high; much of this discrepancy is removed by including additional correlation effects from charge-transfer states. Large Jahn-Teller (JT) splittings of 4T1 and 4T2 levels are found with D2d distortion. Difficulty in accurately evaluating force constants interferes with predicting the corresponding deformations and stabilization energies. Estimates, encorporating the observed Stokes'; shift and JT stabilization energy, are that R(Mn-S) decreases by ∼0.1 Å and the S-Mn-S dihedral angle increases by 7sim;8°, in the lowest quartet level.

Electron correlation effects in small iron clusters

2004 ◽  
Vol 1 (4) ◽  
pp. 288-296 ◽  
Author(s):  
G. Rollmann ◽  
P. Entel
Keyword(s):  
Electron Correlation ◽  
Density Functional ◽  
Magnetic Moments ◽  
Coulomb Repulsion ◽  
Correlation Effects ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Jahn Teller ◽  
Electron Correlation Effects ◽  
Ground State Structures

We present results of first-principles calculations of structural, magnetic, and electronic properties of small Fe clusters. It is shown that, while the lowest-energy isomers of Fe3 and Fe4 obtained in the framework of density functional theory within the generalized gradient approximation (GGA) are characterized by Jahn-Teller-like distortions away from the most regular shapes (which is in agreement with other works), these distortions are reduced when electron correlation effects are considered explicitly as within the GGA+U approach. At the same time, the magnetic moments of the clusters are enhanced with respect to the pure GGA case, resulting in maximal moments (in the sense of Hund’s rules) of 4 μB per atom for the ground state structures of Fe3 and Fe4, and a total moment of 18 μB for Fe5. This already happens for moderate values of the Coulomb repulsion parameter U̴ 2.0 eV and is explained by changes in the electronic structures of the clusters.

Quantifying electron-correlation effects in small coinage-metal clusters by ab initio calculations

2021 ◽  
Author(s):  
Victor Giovanni de Pina ◽  
Bráulio Gabriel Alencar Brito ◽  
Guo -Q Hai ◽  
Ladir Cândido
Keyword(s):  
Monte Carlo ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electron Correlation ◽  
Metal Clusters ◽  
Correlation Effects ◽  
Diffusion Monte Carlo ◽  
Coinage Metal ◽  
Electron Correlation Effects ◽  
Fixed Node

We investigate many-electron correlation effects in neutral and charged coinage-metal clusters Cun, Agn, and Aun (n = 1 − 4) by ab initio calculations using fixed-node diffusion Monte Carlo (FN-DMC)...

BS DFT and BS HDFT studies of CrCr sextuple bond from the viewpoint of electron correlation effects

2009 ◽  
Vol 109 (14) ◽  
pp. 3315-3324 ◽  
Author(s):  
Yasutaka Kitagawa ◽  
Yasuyuki Nakanishi ◽  
Toru Saito ◽  
Takashi Kawakami ◽  
Mitsutaka Okumura ◽  
...  
Keyword(s):  
Electron Correlation ◽  
Correlation Effects ◽  
Electron Correlation Effects

Nonnuclear Maxima in the Charge Density

1993 ◽  
Vol 48 (1-2) ◽  
pp. 127-133 ◽  
Author(s):  
Kenneth E. Edgecombe ◽  
Vedene H. Smith, Jr. ◽  
Florian Müller-Plathe
Keyword(s):  
Charge Density ◽  
Electron Density ◽  
Electron Correlation ◽  
Basis Set ◽  
Valence Shell ◽  
Correlation Effects ◽  
Electron Correlation Effects

Abstract Basis-set and electron-correlation effects on the appearance and disappearance of nonnuclear maxima in the electron density are examined in Li2 , Na2 , Na4 and Na5 . It is shown that nonnuclear attractors can be removed in all cases except Li2 . The appearance of a pseudoatom in a lithium molecule correlates remarkably well with the size of the region, in an atomic calculation, of V2r(r) for the valence shell of the atom. This and the fact that the pseudoatom is also present in the promolecule indicate that the pseudoatoms are remnants of, or in fact are portions of, atoms that are not perturbed enough in the molecule to remove an essentially atomic characteristic.

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