Locality and nonlocality of electronic structures of molecular systems: Toward QM/MM and QM/QM approaches

Knowledge of the electronic structures of atomic and molecular systems deepens our understanding of the desired system. In particular, several information-theoretic quantities, such as Shannon entropy, have been applied to quantify the extent of electron delocalization for the ground state of various systems. To explore excited states, we calculated Shannon entropy and two of its one-parameter generalizations, Rényi entropy of order α and Tsallis entropy of order α , and Onicescu Information Energy of order α for four low-lying singly excited states (1s2s 1 S e , 1s2s 3 S e , 1s3s 1 S e , and 1s3s 3 S e states) of helium. This paper compares the behavior of these three quantities of order 0.5 to 9 for the ground and four excited states. We found that, generally, a higher excited state had a larger Rényi entropy, larger Tsallis entropy, and smaller Onicescu information energy. However, this trend was not definite and the singlet–triplet reversal occurred for Rényi entropy, Tsallis entropy and Onicescu information energy at a certain range of order α .

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Molecular orbitals from group orbitals. I. A perturbational molecular orbital treatment of the electronic structures, shapes and conformations of AHmBHn Systems

Canadian Journal of Chemistry ◽

10.1139/v76-137 ◽

1976 ◽

Vol 54 (6) ◽

pp. 949-962 ◽

Cited By ~ 15

Author(s):

Myung-Hwan Whangbo ◽

Saul Wolfe

Keyword(s):

Molecular Orbital ◽

Electronic Structures ◽

Molecular Orbitals ◽

Orbital Interaction ◽

Molecular Systems ◽

Group Orbitals

A procedure is proposed which allows the group orbitals of a fragment AHm—to be obtained from the molecular orbitals of the molecule AHm—H. Orbital interaction diagrams constructed from these group orbitals have been found useful in the description of the electronic structures and conformations of a variety of molecular systems of the type AHmBHn. The molecules that have been treated by this procedure include ethane, hydrazine, diphosphine, aminophosphine, aminoborane, and sulfonium and phosphonium ylids.

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An ab initio and density functional theory study on neutral pterin radicals

Pteridines ◽

10.1515/pterid-2015-0008 ◽

2015 ◽

Vol 26 (4) ◽

pp. 135-142 ◽

Cited By ~ 4

Author(s):

Gilbert Reibnegger

Keyword(s):

Density Functional Theory ◽

Gas Phase ◽

Electronic Structures ◽

Density Functional ◽

Electron System ◽

Hydrogen Atoms ◽

Functional Theory ◽

Molecular Systems ◽

Phase Water ◽

Planar Transition

AbstractThe electronic structures of the five radicals resulting from homolytic elimination of one of the hydrogen atoms from the most stable tautomeric form of neutral pterin were investigated in gas phase as well as in aqueous solution. Molecular wave functions obtained by density functional theory were analysed by quantum theory of atoms in molecules and electron localisation functions (ELF). Spin densities of the radicals as well as electrostatic potential functions were analysed. Radicals resulting from elimination of N-bonded hydrogen atoms are more stable in comparison with radicals obtained after abstraction of C-bonded hydrogen atoms. N-centred radicals show strong delocalisation of spin density over both heteroaromatic rings; in C-centred radicals delocalisation does not occur. ELF analyses showed that in N-derived radicals particularly the lone electron pair at N2′ is strongly involved into the bicyclic heteroaromatic π-electron system. Thereby, bonding geometry at N2′ in these radicals changes from pyramidal to planar. Transition from gas phase to solution phase (water) generally leads to increased polarity of the structures. Pterin-derived free radicals have been implicated in several biologically important reactions; so this investigation provides first insights into the detailed electronic structures of such molecular systems.

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Stationary conditions of the electronic structures against the extension of molecular systems and their application to the elongation method

The Journal of Chemical Physics ◽

10.1063/1.464648 ◽

1993 ◽

Vol 98 (1) ◽

pp. 534-542 ◽

Cited By ~ 21

Author(s):

Koji Maekawa ◽

Akira Imamura

Keyword(s):

Electronic Structures ◽

Molecular Systems ◽

Elongation Method ◽

Stationary Conditions

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Theoretical investigation of the single and double ionization spectra of M(CO)6, M=W

10.21926/acr.2004010 ◽

2020 ◽

Vol 2 (4) ◽

Author(s):

Behnam Nikoobakht ◽

◽

Gulzari L. Malli ◽

Martin Siegert

Keyword(s):

Electronic Structures ◽

Fock Space ◽

Double Ionization ◽

Ionization Potentials ◽

Final State ◽

Molecular Systems ◽

Consistent Treatment ◽

Cluster Methods ◽

Theoretical Considerations ◽

Good Agreement

In this work, we study the single and double ionization spectra of the M(CO)6,with M =( W and Cr ) complexes by applying the four-component algebraic diagrammatic construction and Fock-space coupled cluster methods to extend earlier studies based on less demanding approaches. The computed single and double ionization potentials are in good agreement comparing with the available experimental results. The electronic structures of the cationic molecular systems are carefully investigated by computing accurately single and double ionization potentials. The final state characterization is relied on group theoretical considerations of the contributing orbitals and allowed for a clear assignment. Energy level diagrams show the effect of spin-orbit (SO) coupling starting from scalar relativistic results and for the heavy representative M(CO)6 with M =( W and Cr ) nonadditivity effects of the SO and electron correlation can be observed requiring a consistent treatment of both contributions.

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The Nature of Oxide Surfaces: Topographic and Electronic Structure

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100150666 ◽

1993 ◽

Vol 51 ◽

pp. 966-967

Author(s):

Dawn A. Bonnell ◽

Yong Liang

Keyword(s):

Transition Metal Oxides ◽

Electronic Structures ◽

Recent Progress ◽

Spatial Localization ◽

Level Of Detail ◽

Scanning Tunneling ◽

Oxide Surfaces ◽

Tunneling Microscopy ◽

Considerable Effort ◽

Complete Understanding

Recent progress in the application of scanning tunneling microscopy (STM) and tunneling spectroscopy (STS) to oxide surfaces has allowed issues of image formation mechanism and spatial resolution limitations to be addressed. As the STM analyses of oxide surfaces continues, it is becoming clear that the geometric and electronic structures of these surfaces are intrinsically complex. Since STM requires conductivity, the oxides in question are transition metal oxides that accommodate aliovalent dopants or nonstoichiometry to produce mobile carriers. To date, considerable effort has been directed toward probing the structures and reactivities of ZnO polar and nonpolar surfaces, TiO2 (110) and (001) surfaces and the SrTiO3 (001) surface, with a view towards integrating these results with the vast amount of previous surface analysis (LEED and photoemission) to build a more complete understanding of these surfaces. However, the spatial localization of the STM/STS provides a level of detail that leads to conclusions somewhat different from those made earlier.

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