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  • 1
    Electronic Resource
    Electronic Resource
    Properties and Stabilities of MX, MX2, and M2X2 Compounds (M = Zn, Cd, Hg; X = F, Cl, Br, I) (1995)
    s.l. : American Chemical Society
    Inorganic chemistry 34 (1995), S. 5597-5605 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00126a033
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  • 2
    Electronic Resource
    Electronic Resource
    Relativistic effects in gold chemistry. I. Diatomic gold compounds (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1762-1774 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Nonrelativistic and relativistic Hartree–Fock (HF) and configuration interaction (CI) calculations have been performed in order to analyze the relativistic and correlation effects in various diatomic gold compounds. It is found that relativistic effects reverse the trend in most molecular properties down the group (11). The consequences for gold chemistry are described. Relativistic bond stabilizations or destabilizations are dependent on the electronegativity of the ligand, showing the largest bond destabilization for AuF (86 kJ/mol at the CI level) and the largest stabilization for AuLi (−174 kJ/mol). Relativistic bond contractions lie between 1.09 (AuH+) and 0.16 A(ring) (AuF). Relativistic effects of various other properties are discussed. A number of as yet unmeasured spectroscopic properties, such as bondlengths (re), dissociation energies (De), force constants (ke), and dipole moments (μe), are predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457082
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  • 3
    Electronic Resource
    Electronic Resource
    Nonspherical atomic ground-state densities and chemical deformation densities from x-ray scattering (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4956-4969 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Presuming that chemical insight can be gained from the difference between the molecular electron density and the superposition of the ground-state densities of the atoms in a molecule, it is pointed out that, for atoms with degenerate ground states, an unpromoted "atom in a molecule'' is represented by a specific ensemble of the degenerate atomic ground-state wave functions and that this ensemble is determined by the anisotropic local surroundings. The resulting atomic density contributions are termed oriented ground state densities, and the corresponding density difference is called the chemical deformation density. The constraints implied by this conceptual approach for the atomic density contributions are formulated and a method is developed for determining them from x-ray scattering data. The electron density of the appropriate promolecule and its x-ray scattering are derived, the determination of the parameters of the promolecule is outlined, and the chemical deformation density is formulated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457713
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  • 4
    Electronic Resource
    Electronic Resource
    Zur Anwendung von Austauschpotentialen bei SCF-Rechnungen an Atomen (1968)
    Springer
    The European physical journal 214 (1968), S. 149-156 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Zusammenfassung Das statistische Austauschpotential berücksichtigt den Selbstaustausch lokalisierter Elektronensysteme nicht ausreichend. Es wird eine einfache Korrektur vorgeschlagen, die dem (außer bei den äußeren Schalen) Rechnung trägt, so daß die Hartree-Fock-Gesamtenergien auf wenige ‰ genau erhalten werden. Weiterhin wird gezeigt, daß schon bei einem 3-Elektronensystem die statistische Näherung zu guter Rumpf-Valenzelektronen-Austauschenergie führt, wenn man die Gombás-Korrektur berücksichtigt; und zwar nicht nur bei direkter Orthogonalisierung des Valenzorbitals auf dem Rumpf, sondern auch bei Besetzungsverbot-Operator-Rechnungen.
    Notes: Abstract The statistical exchange potential does not satisfactorily allow for self-exchange in localized electron systems. A simple correction is proposed which is capable of accounting for this leading to overall Hartree-Fock-energies with an accuracy of a few tenths of a per cent. Furthermore it is shown that even for a three-electron system the statistical approximation gives a good core valence exchange energy correction, if the correction ofGombás is used. This is true not only in the case where the valence orbital is explicitly orthogonalized on the core but also when the occupation exclusion operator formalism is used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01379799
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  • 5
    Electronic Resource
    Electronic Resource
    Die Alkalimetallmoleküle nach dem Kombinierten NÄherungsverfahren (KN) (1969)
    Springer
    Theoretical chemistry accounts 15 (1969), S. 235-243 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Potentialmulden der Moleküle Li2, Na2, K2, Rb2, Cu2 im Grundzustand werden nach dem Kombinierten NÄherungsverfahren (KN, [3]) unter Verwendung von „Hellmann-Potentialoperatoren“ nach einer „Deformierte Atome in Molekülen“-VB-CI-Methode berechnet. Diese und andere Ergebnisse werden hinsichtlich der günstigsten Form des Modellpotentialoperators diskutiert.
    Abstract: Résumé Calcul des courbes de potentiel de Li2, Na2, K2, Rb2 dans leurs états fondamentaux par la méthode du pseudopotentiel de Hellman modifiée, (KN, [3]) à l'aids d'une procédure DAIM. On utilise ces résultats et d'autres pour une discussion de la meilleure forme de l'opérateur potentiel modéle.
    Notes: Abstract The ground state potential curves of Li2, Na2, K2, Rb2, Cu2 near the minima have been calculated with the aid of the modified Hellmann's pseudopotential method (KN, [3]) using a DAIM procedure. These and other results are discussed regarding an optimal form of the model potential operator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00526201
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  • 6
    Electronic Resource
    Electronic Resource
    Modifiziertes Statistisches Atommodell (1971)
    Springer
    Theoretical chemistry accounts 23 (1971), S. 21-38 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die statistische Atomtheorie nach Thomas und Fermi liefert ein fehlerhaftes Verhalten der Elektronendichte bei kleinen Kernabständen. Es wird eine modifizierte statistische Besetzungsvorschrift vorgeschlagen, die hier zu einer Verbesserung führt. Während die einfache Fermi-Statistik nur das Pauliprinzip berücksichtigt, befriedigt die modifizierte Statistik auch die Heisenbergsche Unschärfe-Relation, indem für stark lokalisierte Elektronen Phasenraum-Bereiche mit kleinen Impulsen verboten sind. Die modifizierte Statistik erfordert eine Neubehandlung des statistischen Austauschpotentials. Dichteverteilungen und verschiedene Erwartungswerte werden mit dem neuen Atommodell berechnet und mit exakten Werten verglichen.
    Abstract: Résumé Le modèle statistique de l'atome de Thomas et Fermi conduit à un comportement erroné de la densité électronique au voisinage du noyau. On suggère une règle d'occupation modifiée qui remédie à cette faiblesse du modèle. Alors que la simple statistique de Fermi ne satisfait qu'au principe d'exclusion de Pauli, la statistique modifiée satisfait aussi au principe d'incertitude de Heisenberg, en excluant de l'occupation par des électrons localisés dans l'espace de petits domaines de moment dans l'espace des phases. La statistique modifiée nécessite une nouvelle évaluation du potentiel d'échange statistique. Les distributions de charge atomiques et les valeurs moyennes sont calculées à l'aide de ce nouveau modèle et comparées aux résultats Hartree-Fock.
    Notes: Abstract The statistical atom model of Thomas and Fermi leads to a wrong behaviour of electron density near the nucleus. A modified statistical occupation rule has been suggested, which improves this weakness of the model. Whereas the simple statistics of Fermi only satisfy the Pauli exclusion principle, the modified statistics allows for the Heisenberg uncertainty principle, too, by excluding small momentum domains of the phase space from occupation by spatially localized electrons. The modified statistics necessitate a redetermination of the statistical exchange potential. Atomic charge distributions and expectation values are calculated by the new model and compared with HF-results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00530197
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  • 7
    Electronic Resource
    Electronic Resource
    Das Kombinierte Näherungsverfahren (1968)
    Springer
    Theoretical chemistry accounts 11 (1968), S. 377-384 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Anionen der ersten und neutrale Atome der zweiten Familie des Periodensystems wurden nach dem Kombinierten Näherungsverfahren (KN) mit einem Hellmann-Potential behandelt. Die Fehler in der Hartree-Fock-Energie kompensieren sich auf unter 0.1 eV, ebenso genau wird die Intrahüllenkorrelationsenergie erhalten. Auf Grund der gewonnenen Rechenergebnisse sind als wahrscheinlichste Werte der Elektronenaffinitäten der einwertigen Metalle (in eV) anzusehen: Li 0.63, Na 0.54, K 0.52, Rb 0.50, Cu 1.0.
    Abstract: Résumé Des anions du premier groupe et des atoms neutres du deuxième groupe du système périodique sont traités à l'aide de la méthode „Kombiniertes Näherungsverfahren“ (KN) avec une potential de Hellmann. Les erreurs dans l'énergie SCF se compensent au dessous 0,1 eV, de la même exactitude on obtient l'énergie de correlation de la couche de valence. D'aprés les resultats du calcul on peut accepter les valeurs suivantes comme les plus probables pour les affinités électroniques dans les metaux monovalents (en eV): Li 0,63, Na 0,54, K 0,52, Rb 0,50, Cu 1,0.
    Notes: Abstract Neutral atoms of the second and negative ions of the first family of the periodic system are treated by Hellmann's pseudopotential method (Kombiniertes Näherungsverfahren, KN). The various errors inherent in this method compensate to a large degree so that the errors in the Hartree-Fock and correlation energies will be below 0.1 eV. The electron affinities of the first family atoms are calculated as 0.63 eV for Li, 0.54 for Na, 0.52 for K, 0.50 for Rb, and 1.0 for Cu.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00526654
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  • 8
    Electronic Resource
    Electronic Resource
    Accuracy and limitations of the pseudopotential method (1977)
    Springer
    Theoretical chemistry accounts 44 (1977), S. 61-76 
    Details
    ISSN: 1432-2234
    Keywords: First row elements, di- and triatomic molecules consisting of ∼ ; Pseudopotential method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular model potential calculations have been performed within the SCF approximation on nine di- and triatomic molecules from the first row of the periodic table. We compare the molecular constants with ab initio SCF values and with model potential results obtained by other authors. Our results are accurate to a few per cent. The three most significant approximations in molecular model potential theory are: 1) The molecular model potential is the sum of atomic model potentials; 2) The atomic model potential is energy-independent; 3) The electron interaction model operator is l/r 12. We arrive at the following general conclusions concerning these approximations: 1) The first approximation does not hold for strongly ionic molecules and for some highly excited molecular states. 2) Approximations 2 and 3 cancel to a large extent in molecules as they do in atoms, except in the case where approximation 1 breaks down. 3) Although various model- and pseudo-potentials yield reasonable results for atoms, not all of them are suitable for molecular calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00548029
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  • 9
    Electronic Resource
    Electronic Resource
    The general form of pseudopotential operators (1971)
    Springer
    Theoretical chemistry accounts 23 (1971), S. 147-154 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die allgemeine Form hermitescher linearer Pseudopotentialoperatoren, die die virtuellen Orbitalenergien nicht enthalten, wird angegeben. Eine spezielle Form hiervon ist das üblicherweise verwendete Potential ¦c〉(ɛ−ɛ c)〈c¦. Es wird gezeigt, da\ jegliches Pseudopotential wesentlich nichtlokalen Charakter hat. Die Bedeutung von s-AbhÄngigkeit und Nicht-HermitezitÄt von Pseudopotentialen wird diskutiert. Der Vorzug von Modell-Hamiltonoperatoren gegenüber exakten Pseudo-Operatoren wird betont.
    Abstract: Résumé Expression générale des opérateurs de pseudo-potentiel linéaires hermitiques, indépendants des énergies des orbitales virtuelles. Le pseudo-potentiel ordinairement utilisé ¦c〉(ɛ−ɛ c)〈c¦ en est un cas particulier. On montre que tout pseudo-potentiel a essentiellement un caractère non local. Discussion de la signification de la dépendance à ɛ et de la non-hermiticité des pseudo-potentiels. On souligne les avantages des hamiltoniens modèles semi-empiriques par rapport aux hamiltoniens de pseudo-potentiel exact.
    Notes: Abstract The general form of hermitean linear pseudopotential operators, which are independent of the virtual energies, is derived. A special case of this pseudopotential is the usually used one, ¦c〉(ɛ−ɛ c)〈c¦. It is shown that any pseudopotential is of essentially non-local character. The significance of ɛ-dependency and non-hermiticity of pseudopotentials is discussed. The advantages of semiempirical model hamiltonians in comparison with exact pseudopotential hamiltonians are stressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00526428
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  • 10
    Electronic Resource
    Electronic Resource
    Gombás pseudopotential SCF calculations for atoms (1972)
    Springer
    Theoretical chemistry accounts 24 (1972), S. 29-34 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Das sog. „Vereinfachte SCF-Verfahren“ von Gombás, bei welchem die Orthogonalitätsbedingungen der Orbitale durch statistische Pseudopotentiale ersetzt werden, wird erstmalig durch saubere numerische Rechnungen getestet. Während die unkorrigierte Version der Methode Resultate mit charakteristischen Fehlern liefert, führt der kürzlich von Gombás abgeleitete Korrekturfaktor im Besetzungsverbotpotential zu überraschend guten Ergebnissen.
    Abstract: Résumé La «méthode SCF simplifiée» de Gombás, où les conditions d'orthogonalité des orbitales sont remplacées par des pseudo potentiels statistiques, a été pour la première fois éprouvée avec des calculs numériques précis sans aucune autre approximation. Alors que la version originale de la méthode conduit à des tendances d'erreurs caractéristiques, un facteur de correction récemment introduit par Gombás dans l'expression du pseudo-potential, produit des résultats remarquablement bons.
    Notes: Abstract The “Simplified SCF Method” of Gombás, in which the orbital orthogonality conditions are replaced by statistical pseudopotentials, has been tested for the first time by accurate numerical calculations without any further approximation. Whereas the original version of the method leads to characteristic error trends, a correction factor recently introduced by Gombás into the pseudopotential expression, produces surprisingly good results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00528307
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