International Journal of Quantum Chemistry

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Molecular structures, thermochemistry, and electron affinities for the dichlorine oxides: Cl2On/Cl2O (n = 1–4)
International Journal of Quantum Chemistry - Tập 95 Số 6 - Trang 731-757 - 2003
Qian‐Shu Li, Shun-feng Lü, Yaoming Xie, Paul von Ragué Schleyer, Henry F. Schaefer
AbstractThe molecular structures, relative energies, vibrational frequencies, and electron affinities for the Cl2On/Cl2O (n = 1–4) systems have been investigated using hybrid Hartree–Fock/density functional theories (BHLYP and B3LYP) and pure density functional theories (BP86 and BLYP). The three different types of neutral/anion energy differences reported in this research are the adiabatic electron affinity (EAad), the vertical electron affinity (EAvret), and the vertical detachment energy (VDE). The basis set used in this work is of double‐ζ plus polarization quality with additional s‐ and p‐type diffuse functions, and it is denoted DZP++. The geometries are fully optimized by all four DFT methods. We have predicted a number of possible low‐lying local minima, including some that are unprecedented. Most strikingly, in several cases structures that have been observed in the laboratory turn out not to be lowest in energy for a particular chemical composition. Two structures are predicted with a formally seven‐coordinate chlorine atom. The global minima for the Cl2On/Cl2O (n = 1–4) systems are ClOCl (C2v), ClClO− (Cs), ClOOCl (C2), OOCl (C2v), ClOOOCl (C2/C1), ClO(O2)Cl− (Cs), trans‐ClO(O2)OCl (Ci), and trans‐ClO(O2)OCl− (Ci), respectively. The relative energies of the different minima are reported. Five of the 42 structures predicted here have been determined experimentally. Our theoretical geometries and vibrational frequencies are carefully compared with the limited available experimental results, and the BHLYP functional in general provides the best agreement. The ClClO− and ClClO hiện toàn bộ
Blue‐shifted and red‐shifted hydrogen bonds: Theoretical study of the CH3CHO· · ·HNO complexes
International Journal of Quantum Chemistry - Tập 106 Số 5 - Trang 1199-1207 - 2006
Yong Yang, Weijun Zhang, Xiaoming Gao
AbstractThe blue‐shifted and red‐shifted H‐bonds have been studied in complexes CH3CHO…HNO. At the MP2/6‐31G(d), MP2/6‐31+G(d,p) MP2/6‐311++G(d,p), B3LYP/6‐31G(d), B3LYP/6‐31+G(d,p) and B3LYP/6‐311++G(... hiện toàn bộ
Improved intermolecular SCF theory and the BSSE problem
International Journal of Quantum Chemistry - Tập 36 Số 3 - Trang 225-240 - 1989
I. Mayer, Péter R. Śurján
AbstractAnalytical and numerical studies are performed concerning the exclusion of the basis set superposition error (BSSE) from the SCF calculations of intermolecular interactions. Based on these studies a new procedure is proposed, which consists of the following steps: (1) determine the orbitals by the SCF...... hiện toàn bộ
Simplification of the CBS‐QB3 method for predicting gas‐phase deprotonation free energies
International Journal of Quantum Chemistry - Tập 110 Số 2 - Trang 323-330 - 2010
Rodrigo Casasnovas, Juan Frau, Joaquín Ortega‐Castro, Antoni Salvà, Josefa Donoso, Francisco Muñoz
AbstractSimplified versions of CBS‐QB3 model chemistry were used to calculate the free energies of 36 deprotonation reactions in the gas phase. The best such version, S9, excluded coupled cluster calculation [CCSD(T)], and empirical (ΔEemp) and spin‐orbit (ΔEint) correct...... hiện toàn bộ
A polarization propagator analysis of through-space spin-spin coupling constants:19F-19F couplings
International Journal of Quantum Chemistry - Tập 30 Số S20 - Trang 585-601 - 1986
Martín C. Ruiz de Azúa, A. C. Diz, Claudia G. Giribet, Rubén H. Contreras, Ian D. Rae
Transmission mechanisms of spin–spin coupling constants within the CHF approximation: Their study using inner projections of the polarization propagator
International Journal of Quantum Chemistry - Tập 23 Số 3 - Trang 1033-1045 - 1983
Alejandro R. Engelmann, Rubén H. Contreras
AbstractA new method for separating differently transmitted components of spin–spin coupling constants is introduced which is suitable when couplings are calculated using the coupled Hartree–Fock (CHF) approximation via the polarization propagator. Contributions transmitted through different electronic subsystems are found choosing different subsets of orbitals wit...... hiện toàn bộ
The use of localized molecular orbitals and the polarization propagator to identify transmission mechanisms in nuclear spin‐spin couplings
International Journal of Quantum Chemistry - Tập 37 Số 5 - Trang 663-677 - 1990
A. C. Diz, Martín C. Ruiz de Azúa, Claudia G. Giribet, Rubén H. Contreras
AbstractAn extension of the IPPP (inner projections of the polarization propagator) method to theoretically analyze transmission mechanisms of indirect nuclear spin‐spin couplings is presented. The localization technique used is modified so that all the canonical molecular orbitals of a compound may be localized to repr...... hiện toàn bộ
A progress report on the status of the COLUMBUSMRCI program system
International Journal of Quantum Chemistry - Tập 34 Số S22 - Trang 149-165 - 1988
Ron Shepard, Isaiah Shavitt, Russell M. Pitzer, Donald C. Comeau, M. Pepper, Hans Lischka, Péter G. Szalay, Reinhart Ahlrichs, Franklin B. Brown, Jingtao Zhao
Ab initio molecular orbital calculation of fe‐porphine with a double zeta basis set
International Journal of Quantum Chemistry - Tập 20 Số 4 - Trang 843-859 - 1981
Hiroshi Kashiwagi, Shigeru Obara
AbstractAn ab initio LCAO SCF MO calculation was performed on planar Fe‐porphine with a double zeta basis set consisting of 300 CGTO's. SCF wave functions of several states of Fe‐porphine and its cation were obtained. The net charge of Fe is in the range of 1.39 to 1.53. The highest...... hiện toàn bộ
Interpretation of the vibrational spectra of matrix‐isolated uracil from scaled ab initio quantum mechanical force fields
International Journal of Quantum Chemistry - Tập 29 Số 4 - Trang 799-815 - 1986
L Harsányi, Pál Császár, Attila G. Császár, James E. Boggs
AbstractThe vibrational spectrum of uracil trapped in an argon matrix has been interpreted based on ab initio Hartree–Fock SCF calculations with a split‐valence 4‒21 basis set. The directly computed theoretical general valence force field was scaled with empirical scale factors in order to correct for the systematic errors originating in the limitation of the theor...... hiện toàn bộ
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