Journal ArticleDOI
Ab Initio MRD‐CI Calculations for HAB Molecules I. Isomerization Energies for HOS, HNP and HCSi and Their Positive Ions
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TLDR
In this paper, a series of ab initio calculations is reported which employs the MRD-CI method in a standard AO basis of double-zeta plus polarization quality for the HSO-HOS, HPN-HNP and HSiC-HCSi isomers and their corresponding positive ions.Abstract:
A series of ab initio calculations is reported which employs the MRD-CI method in a standard AO basis of double-zeta plus polarization quality for the HSO-HOS, HPN-HNP and HSiC-HCSi isomers and their corresponding positive ions. The equilibrium geometries of each of these twelve systems has been carefully optimized (in some cases in a variety of low-lying electronic states) and the structural results are found to be in substantial agreement with the qualitative predictions of the Mulliken-Walsh MO model, although some significant deviations from this general pattern are indicated for certain of the more relatively unstable isomeric species. Unusually large isomerization energies are calculated in a number of instances and a strong preference for structures with the second-row atom at the terminal position of the molecule is noted generally. The largest and smallest distinctions in the relative stabilities of the isomers studied to date are found to occur for systems with 10 and 12 valence electrons respectively (110 kcal/mole for HCS+-HSC+ and 2 kcal/mole for ‘A’ HOS+-HSO+, for example) and from a survey of such findings it is concluded that each type of molecular orbital exhibits a characteristic effect on the magnitude of these energy differences. Finally it is pointed out that in isovalent series isomerization energies tend to increase with the electronegativity of the second-row atom in HAB systems of mixed first- and second-row composition.read more
Citations
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π-Bonding and the Lone Pair Effect in Multiple Bonds between Heavier Main Group Elements
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Computational chemistry: a useful (sometimes mandatory) tool in mass spectrometry studies.
TL;DR: The usefulness of ab initio or density functional theory (DFT) methods to predict the existence of elusive molecules and/or to characterize non-conventional structures, and to rationalize the charge redistributions normally associated with ion-molecule interactions and which result in bond-weakening or bond-reinforcement effects are illustrated.
Journal ArticleDOI
Reactive scattering of atoms and radicals
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TL;DR: In this article, the authors give a brief overview of the recent progress in the field of reaction dynamics and then survey recent work from our laboratory on reactions of atoms and radicals with simple molecules by the crossed molecular beam scattering method using mass-spectrometric detection.
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Arylmino(halogeno)phosphanes XPNC6H2tBu3 (X Cl, Br, I) and the Iminophosphenium Tetrachloroaluminate [PNC6H2tBu3]⊕[AlCl4]⊖: the First Stable Compound with a PN Triple Bond
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Theoretical prediction of the potential curves for the lowest‐lying states of the CSi+ and Si2+ molecular ions
TL;DR: In this paper, the MRD-CI potential curves have been calculated for C2+ in its first 16 electronic states and vertical transition energies Tv have been computed for a number of higher-lying species, all of which correlate with the first dissociation limit C(3Pg)+C+(2Pu).
References
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Journal ArticleDOI
Gaussian Basis Functions for Use in Molecular Calculations. III. Contraction of (10s6p) Atomic Basis Sets for the First‐Row Atoms
TL;DR: In this paper, the effects of contraction on the energies and one-electron properties of the water and nitrogen molecules were investigated, and the authors obtained principles which can be used to predict optimal contraction schemes for other systems without the necessity of such exhaustive calculations.
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Gaussian‐Type Functions for Polyatomic Systems. II
Sigeru Huzinaga,Catalina Arnau +1 more
TL;DR: In this article, the use of a linear combination of Gaussian type orbitals (CGTO) instead of an individual Gaussian-type orbital (GTO) as a unit of basis functions for large-scale molecular calculations is discussed.
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Configuration interaction calculations on the nitrogen molecule
TL;DR: In this article, a contracted Gaussian basis set capable of describing about 63% of the correlation energy of N2 has been used in a detailed configuration-interaction calculation, and second-order perturbation theory overestimated the correlated energy by 23-50% depending on how H0 was chosen.
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Individualized configuration selection in CI calculations with subsequent energy extrapolation
TL;DR: In this paper, a configuration selection method for CI calculations is discussed and applied in which the energy lowering produced in a secular equation by the addition of a given test species to a series of dominant configurations is used as an ordering parameter.
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Applicability of the multi-reference double-excitation CI (MRD-CI) method to the calculation of electronic wavefunctions and comparison with related techniques
TL;DR: In this article, a multi-reference double-excitation CI (MRD-CI) method is discussed and its results are compared with those of related techniques, which employs a configuration selection procedure to order the various generated species according to their energy-lowering capability and then uses an energy extrapolation procedure based on perturbation theory to obtain suitably accurate estimates of the eigenvalues of the entire MRD- CI space.