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  • 1
    Electronic Resource
    Electronic Resource
    Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions (1990)
    Springer
    Theoretical chemistry accounts 77 (1990), S. 291-306 
    Details
    ISSN: 1432-2234
    Keywords: Atomic natural orbitals ; Basis sets ; General contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Generally contracted basis sets for first row atoms have been constructed using the Atomic Natural Orbital (ANO) approach, with modifications for allowing symmetry breaking and state averaging. The ANOs are constructed by averaging over several atomic states, positive and negative ions, and atoms in an external electric field. The contracted basis sets give virtually identical results as the corresponding uncontracted sets for the atomic properties, which they have been designed to reproduce. The design objective has been to describe the ionization potential, the electron affinity, and the polarizability as accurately as possible. The result is a set of well-balanced basis sets for molecular calculations. The starting primitive sets are 8s4p3d for hydrogen, 9s4p3d for helium, and 14s9p4d3f for the heavier first row atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01120130
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  • 2
    Electronic Resource
    Electronic Resource
    Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions (1995)
    Springer
    Theoretical chemistry accounts 90 (1995), S. 87-114 
    Details
    ISSN: 1432-2234
    Keywords: Atomic natural orbitals ; Basis sets ; General contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Generally contracted Basis sets for the atoms H-Kr have been constructed using the atomic natural orbital (ANO) approach, with modifications for allowing symmetry breaking and state averaging. The ANO's are constructed by averaging over the most significant electronic states, the ground state of the cation, the ground state of the anion for some atoms and the homonuclear diatomic molecule at equilibrium distance for some atoms. The contracted basis sets yield excellent results for properties of molecules such as bond-strengths and-lengths, vibrational frequencies, and good results for valence spectra, ionization potentials and electron affinities of the atoms, considering the small size of these sets. The basis sets presented in this article constitute a balanced sequence of basis sets suitable for larger systems, where economy in basis set size is of importance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113842
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  • 3
    Electronic Resource
    Electronic Resource
    Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions (1995)
    Springer
    Theoretical chemistry accounts 92 (1995), S. 149-181 
    Details
    ISSN: 1432-2234
    Keywords: Basis sets ; Atomic natural orbitals ; General contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Generally contracted basis sets for the first row transition metal atoms Sc-Zn have been constructed using the atomic natural orbital (ANO) approach, with modifications for allowing symmetry breaking and state averaging. The ANOs are constructed by averaging over the three electronic configurationsd n ,d n−1 s, andd n−2 s 2 for the neutral atom as well as the ground state for the cation and the ground state atom in an external electric field. The primitive sets are 21s15p10d6f4g. Contraction to 6s5p4d3f2g yields results that are virtually identical to those obtained with the corresponding uncontracted basis sets for the atomic properties, which they have been designed to reproduce. Slightly larger deviations are obtained with the 5s4p3d2f1g for the polarizability, while energetic properties still have only small errors. The design objective has been to describe the ionization potential, the polarizability and the valence spectrum as accurately as possible. The result is a set of well-balanced basis sets for molecular calculations, which can be used together with basis sets of the same quality for the first and second row atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01114922
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  • 4
    Electronic Resource
    Electronic Resource
    A quantum chemical study of the hydrogen bonding in the CO2⋯HF and N2O⋯HF complexes (1989)
    Springer
    Theoretical chemistry accounts 76 (1989), S. 173-185 
    Details
    ISSN: 1432-2234
    Keywords: Hydrogen bonding ; CO2-HF complex ; N2O-HF complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Quantum chemical ab initio calculations have been performed for the complex CO2⋯HF and N2O⋯HF. The interaction energies were computed through fourth order MBPT and were corrected for basis set superposition errors. Extended polarized basis sets were used which are constructed to give accurate values for electric moments and polarizabilities. The complex NNO⋯HF was found to be bent, while OCO⋯HF is linear, in agreement with experiment. The MBPT calculations give evidence for a second linear isomeric structure FH⋯NNO, a possibility which has also been suggested by recent experimental data. The computed binding energies are: 2.5 kcal/mol for OCO⋯HF, 2.4 kcal/mol for NNO⋯HF, and 3.0 kcal/mol for FH⋯NNO. At the SCF level, the FH⋯NNO complex is less stable than NNO⋯HF, but correlation has a large effect on the geometry and energetics of the latter complex. The NNO⋯HF complex seems to be a system where the positive intramolecular correlation correction prevails over the negative intermolecular component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527471
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  • 5
    Electronic Resource
    Electronic Resource
    SCF-CI studies of the equilibrium structure and the proton transfer barrier H3O 2 − (1976)
    Springer
    Theoretical chemistry accounts 42 (1976), S. 77-82 
    Details
    ISSN: 1432-2234
    Keywords: Configuration interaction ; Hydrogen bonding ; Ion hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Large-scale configuration interaction (CI) calculations have been performed in order to study the effect of the correlation energy on the equilibrium geometrical structure, the stability, and on the energy barrier of the proton transfer reaction in the hydrogen bonded system HO− · HOH. An extended Gaussian basis set including polarization functions on each nuclear centre has been employed to approximate the molecular Orbitals. All possible single and double replacements resulting from a single determinant Hartree-Fock reference state have been taken into account in the CI wavefunction. Compared to the SCF results the equilibrium oxygen/oxygen distance has been obtained from the CI calculations to be smaller by about 0.08 Å and the correlation energy has been found to stabilize the composed system by 3.6 kcal/mole. An almost symmetric equilibrium structure with the hydrogen bonding H-atom midway between the two oxygen centres has been obtained in the CI treatment, whereas SCF calculations yield an asymmetric geometrical configuration with a small energy barrier of 1.4 kcal/mole for the proton transfer process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00548292
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  • 6
    Electronic Resource
    Electronic Resource
    SCF-CI studies of correlation effects on hydrogen bonding and ion hydration (1975)
    Springer
    Theoretical chemistry accounts 36 (1975), S. 249-274 
    Details
    ISSN: 1432-2234
    Keywords: Configuration interaction ; Hydrogen bonding ; Ion hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Previous single-determinant Hartree-Fock studies on the equilibrium structures and stabilities of H2 O, H3 O+ as well as of the monohydrated ionic systems Li+ · H2O, F− · H2O and the hydrogen bonded water dimer, H2 O · HOH, are extended by large scale configuration interaction calculations including all the possible single and double excitations arising from the canonical set of Hartree-Fock molecular orbitals. The correlation energy effects on the equilibrium geometrical parameters of the systems under consideration are found to be quite small. The contributions of the correlation energy to the total binding energies of the weakly interacting composed systems are obtained to be of the order of 1 kcal/mole, leading to a considerable increase of the hydrogen bond strength in F− · H2O and H2O · HOH and to a small decrease of the binding energy in Li+ · H2 O. The observed strengthening of the hydrogen bonding interaction due to correlation is shown to be partly compensated by the change in the vibrational zero-point energy of the composed systems compared to the non-interacting subsystems. Approximate force constants corresponding to the intersystem vibrations in Li+ · H2O, F− · H2 O, and H2O · HOH are deduced from the calculated potential curve data on the SCF and the CI level of accuracy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00549690
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  • 7
    Electronic Resource
    Electronic Resource
    Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions IV. Medium size basis sets for the atoms H—Kr (1995)
    Springer
    Theoretica chimica acta 90 (1995), S. 87-114 
    Details
    ISSN: 0040-5744
    Keywords: Key words: Atomic natural orbitals ; Basis sets ; General contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  Generally contracted Basis sets for the atoms H–Kr have been constructed using the atomic natural orbital (ANO) approach, with modifications for allowing symmetry breaking and state averaging. The ANO’s are constructed by averaging over the most significant electronic states, the ground state of the cation, the ground state of the anion for some atoms and the homonuclear diatomic molecule at equilibrium distance for some atoms. The contracted basis sets yield excellent results for properties of molecules such as bond-strengths and -lengths, vibrational frequencies, and good results for valence spectra, ionization potentials and electron affinities of the atoms, considering the small size of these sets. The basis sets presented in this article constitute a balanced sequence of basis sets suitable for larger systems, where economy in basis set size is of importance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113842
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  • 8
    Electronic Resource
    Electronic Resource
    Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions III. First row transition metal atoms (1995)
    Springer
    Theoretica chimica acta 92 (1995), S. 149-181 
    Details
    ISSN: 0040-5744
    Keywords: Key words: Basis sets ; Atomic natural orbitals ; General contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract.  Generally contracted basis sets for the first row transition metal atoms Sc–Zn have been constructed using the atomic natural orbital (ANO) approach, with modifications for allowing symmetry breaking and state averaging. The ANOs are constructed by averaging over the three electronic configurations d n , d n-1 s,  and d n-2 s 2 for the neutral atom as well as the ground state for the cation and the ground state atom in an external electric field. The primitive sets are 21s15p10d6f4g. Contraction to 6s5p4d3f2g yields results that are virtually identical to those obtained with the corresponding uncontracted basis sets for the atomic properties, which they have been designed to reproduce. Slightly larger deviations are obtained with the 5s4p3d2f1g for the polarizability, while energetic properties still have only small errors. The design objective has been to describe the ionization potential, the polarizability and the valence spectrum as accurately as possible. The result is a set of well-balanced basis sets for molecular calculations, which can be used together with basis sets of the same quality for the first and second row atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01114922
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