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  • AO  (1)
  • Arsenidokomplexe  (1)
  • Crystal  (1)
  • Inorganic Chemistry  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 87 (1993), S. 147-173 
    ISSN: 1432-2234
    Keywords: Correlation ; MP2 ; AO ; Laplace transform ; Bounds ; Parallel computer ; Gradient ; Crystal ; Solid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A novel formulation of MP2 theory is presented which starts from the Laplace transform MP2 ansatz, and subsequently moves from a molecular orbital (MO) representation to an atomic orbital (AO) representation. Consequently, the new formulation is denoted AO-MP2. As in traditional MP2 approaches electron repulsion integrals still need to be transformed. Strict bounds on the individual MP2 energy contribution of each intermediate four-index quantity allow to screen off numerically insignificant integrals with a single threshold parameter. Implicit in our formulation is a bound to two-particle density matrix elements. For small molecules the computational cost for AO-MP2 calculations is about a factor of 100 higher than for traditional MO-based approaches, but due to screening the computational effort in larger systems will only grow with the fourth power of the size of the system (or less) as is demonstrated both in theory and in application. MP2 calculations on (non-metallic) crystalline systems seem to be a feasible extension of the Laplace transform approach. In large molecules the AO-MP2 ansatz allows massively parallel MP2 calculations without input/output of four-index quantities provided that each processor has in-core memory for a limited number of two-index quantities. Energy gradient formulas for the AO-MP2 approach are derived.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-8249
    Keywords: Arsenidokomplexe ; Komplexe mit Pnictidliganden ; Phosphidokomplexe ; Wolframverbindungen ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 258-286 
    ISSN: 0044-2313
    Keywords: Structures of phosphorus (amorphous, red, white, Hittorf, cluster, allotrope, phosphane, phosphide) ; ab initio calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Theoretische Untersuchung der strukturellen Systematik kovalenter PhosphorgerüsteAufbauend auf Arbeiten von Baudler wird eine Heuristik zur systematischen Herleitung und Klassifizierung kovalenter Phosphorgerüststrukturen in polycyclischen Phosphanen, phosphorreichen Phosphiden und Elementstrukturen des Phosphors (mit Ausnahme der schwarzen Allotrope) eingeführt. Von dieser Systematik geleitet werden mit Ab-initio-Methoden noch unbekannte molekulare oder makromolekulare Formen vor allem des elementaren Phosphors untersucht und mit Hittorfschem Phosphor und mit P4 verglichen. Das Auftreten der letztgenannten Elementstrukturen wird erklärt, die mögliche Existenz einer weiteren kristallinen allotropen Form bestätigt und die wahrscheinliche Struktur des amorphen (roten) Phosphors diskutiert. Insgesamt erschließt die vorgestellte Kombination von chemischer Heuristik mit umfangreichen Ab-initio-Rechnungen ein zusammenhängendes Verständnis von Energetik und Aufbau kovalenter Strukturen (nicht nur) des elementaren Phosphors.
    Notes: Starting from earlier work by Baudler we introduce a chemical heuristic for the systematic deduction and classification of covalent partial structures of phosphorus in polycyclic phosphanes, phosphorus-rich polycyclic phosphides, and allotropes of phosphorus except the black forms. This approach is used to direct ab initio techniques (which also confirm the rules) in the quest for as yet unknown forms of molecular or macromolecular phosphorus. Based on calculated stabilities of systematically generated structural alternatives we rationalize the stabilities of Hittorf's phosphorus and of molecular P4, confirm the possible existence of at least one other crystalline allotropic form of phosphorus, and provide insight into the probable structure of amorphous red phosphorus. In total, the combined approach of chemical heuristics and large scale ab initio calculations presented in this work supplies a coherent chemical understanding of covalent polyphosphorus structures.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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