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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 11315-11322 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reactions of Cd(1S:5s2,3,1P:5s15p1) and Hg(1S:6s2,3,1P:6s16p1) with SiH4 have been studied through multiconfiguration self-consistent-field (MCSCF) (with relativistic effective core potentials) followed by extensive variational and perturbational second-order multireference Möller–Plesset configuration interaction by perturbation selected by iterative process (CIPSI) calculations using extended Gaussian basis sets. It was found that both metal atoms in their 3P(ns1np1) state break the Si–H bond of silane spontaneously, leading directly to the MH+SiH3 final products, in agreement with the experimental results of this reaction for Cd. One important qualitative difference between the Cd and Hg(3P) reactions is that for the former an unstable intermediate was found, whereas for the latter no intermediate exists at all. Again, for both atoms, the 1P(ns1np1) state is also inserted in the Si–H bond and the corresponding interaction surface shows an avoided crossing with the lowest-lying X1A′ potential surface, adiabatically correlated with the M(1S:ns2)+SiH4 reactants. This interaction leads eventually to the MH+SiH3 products. The structure of these HMSiH3 intermediates, diabatically correlated with the M(1P:ns1np1)+SiH4 reactants, was carefully studied, as well as the dissociation channels leading to the MH+SiH3 and H+MSiH3 products. Accurate energy differences between all these species are also reported. The theoretical results obtained for the mercury reaction are discussed in light of the very recent experimental results of Legay-Sommaire and Legay [J. Phys. Chem. A 102, 8579 (1998)] for the insertion of Hg(3P:4s14p1) in SiH4 over N2 and rare gas matrices. Our results confirm their conclusion that the photochemical insertion of Hg(3P) into the Si–H bond of silane proceeds without any activation barrier. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 6627-6633 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reactions of Zn(1S, 3P, and 1P) with SiH4 have been studied through multiconfigurational self-consistent field (with relativistic effective core potentials) followed by extensive variational and perturbational second-order multireference Möller–Plesset configuration interaction by perturbation selected by iterative process calculations using extended Gaussian basis sets. The Zn atom in the 3P(4s14p1) state breaks the Si–H bond of silane spontaneously, leading directly to the ZnH+SiH3 final products, in agreement with experimental results. The 1P(4s14p1) Zn atom is also inserted in the Si–H bond and the corresponding interaction surface shows an avoided crossing with the lowest-lying X 1A′ potential surface, adiabatically correlated with the Zn(1S:4s2)+SiH4 reactants. This interaction leads also to the ZnH+SiH3 products. The structure of the HZnSiH3 intermediate product was carefully studied as well as the dissociation channels leading to the ZnH+SiH3 and H+ZnSiH3 products. Accurate energy differences between these species are also reported. The qualitative difference in the behavior of the 3P(4s14p1) Zn reaction with methane and silane has been explained by analyzing the corresponding potential energy surfaces; the present results confirm the C–H bond steric hindrance hypothesis advanced by Wang et al. [J. Chem. Phys. 104, 9401 (1996)]. © 1997 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 207-215 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the PtSn system with the hydrogen molecule is studied theoretically. The results are compared with experimental reports of commercial-type catalysts and previous theoretical studies of Pt + H2 and Pt2 + H2 reactions. All the calculations were made by the ab initio MC-SCF + MRCI method including relativistic core potentials approximation. We consider two main geometrical approaches of the hydrogen molecule to the SnPt system: parallel and perpendicular. The theoretical and geometrical parameters were taken from our previous studies and from experiments. Many states were studied: Some of them are repulsive and others present weak capture of hydrogen; none scisse the H2 molecule. The main conclusion of this work is that the platinum activity, when Pt and Sn form alloys, is inhibited by the tin, suggesting that the interaction between the two metals occurs through an oxygen atom of the support. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 67 (1998), S. 399-409 
    ISSN: 0020-7608
    Keywords: Au ; Pt ; H2 adsorption ; AuPt clusters ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Linear and triangular AuPtn cluster reactions with H2 are studied theoretically, using ab initio multiconfiguration self-consistent field (MC-SCF) calculations, followed by extensive multireference configuration interaction (MR-CI) variational and perturbative. Both the linear dimer and the triangular trimers capture the hydrogen molecule by the Pt cluster side and by the Au cluster side. Gold has an electronic effect on the Pt activity, more important than a geometrical one, poisoning the Pt activity to dissociate H2 and lowering the adsorption heats. This effect is stronger in the AuPt dimer, where the H2 capture occurs only at the molecular level, without showing hydrogen bond dissociation. The trimers look more active, relaxing the H(SINGLE BOND)H bond until breakage. No activation barriers are observed in all the cases considered. The hydrogen molecule is not able to cross the clusters due to the large barriers present.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 399-409, 1998
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 29-45 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The H2 interaction with the Pd dimer and trimer were studied using multiconfigurational self-consistent field (MC-SCF) calculations with the relativistic effective core potential (RECP); the correlation energy correction was included in the extended multireference configuration interaction (MRCI), variational and perturbative to second order. Here, we considered the Pd2 first six states: 3Σ+u, 1Σ+g, 3Πg, 3Δxy, 1Σ+u, and 3Σ+g. For them, the four geometrical approaches included were the side-on H2 toward Pd2, for the hydrogen molecule in and out the Pd dimer plane; the perpendicular end-on H2 toward Pd2; and the perpendicular end-on Pd2 to H2. The Pd2 ground state is 3Σ+u, which only captures H2 in the C2v end-on approach, softly relaxing the H(SINGLE BOND)H bond. The closed-shell 1Σ+g captures the H2 molecule in all the approaches considered: The side-on approach of this state presents deep wells and relaxes the H(SINGLE BOND)H bond, and the end-on approach captures H2 with a relatively longer H(SINGLE BOND)H distance and also a deep well. The 3Πg state was the only one which did not capture H2. For the triangular Pd3 clusters, H2 was approached in the C2v symmetry in and out of the Pd3 plane. In the triangular case, H2 was absorbed in both spin states, with deep wells and relaxing the H(SINGLE BOND)H distance. The linear Pd3 singlet and triplet states capture outside of the Pd3 and break the H(SINGLE BOND)H bond. © 1997 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 70 (1998), S. 1029-1035 
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The basic and fundamental mechanisms governing the catalytic reaction of small iridium clusters with H2 are presented here with the purpose to determine its behavior in hydrogenation reactions. The iridium dimer/s lowest states in interaction with H2 potential energy surface were obtained using ab initio multiconfigurational self-consistent-field calculations (MC-SCF), with relativististic pseudopotentials. The electronic correlation contribution was included by configurations interaction (CI) calculations, which considered a variational part plus a second-order perturbative part. The Ir2+H2 reactions were developed in the C2v symmetry. The Ir2's five lowest electronic states were determined, 5Πg, 3Πg, 1Σg+, 3Σu+, and 5Σg, and studied when reacted with H2. It was found that the iridium dimer, in these five states, might capture and break the H—H bond, spontaneously in certain cases and after surmounting activation barriers in other cases.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 1029-1035, 1998
    Additional Material: 6 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 549-557 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The C2v potential energy surfaces for the end-on and side-on approaches of H2 to the rhodium dimer were studied through self-consistent-field (SCF) and multiconfigurational SCF calculations, followed by extensive variational plus second-order multireference Møller-Plesset perturbational configuration interaction (CIPSI) calculations. Relativistic effective core potentials were used to replace the core electrons of the rhodium atoms. Together with the Rh2—H2 interaction, the spectroscopic constants for the 5Σg+, 1Σg+, 3Πu, and 1Πu states of Rh2 are reported. We found that the potential energy curves of the parallel and the perpendicular Rh2(5Σg) interaction with H2 show that the rhodium dimer has the ability to capture and break the H2 molecule. The parallel interaction presents a soft potential barrier of 7.8 kcal/mol, energy necessary to surmount before the capture and breaking of the H—H bond. In the perpendicular interaction, we found that Rh2 captures and breaks spontaneously H2. The potential energy curve of the parallel Rh2(1Σg) + H2 interaction shows that Rh2 also captures and breaks spontaneously the H2, with a very deep well of 92.7 kcal/mol, while in the perpendicular approach, we found that Rh2 has to surmount again a soft barrier of 5.2 kcal/mol to capture and break the H2 molecule. Finally, the energy curves of the parallel (Rh2(1,3Πu) + H2) interactions present capture and breaking with very small barriers. The perpendicular interactions capture and scisse the hydrogen molecule spontaneously. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Tab.
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  • 9
    Publication Date: 1999-07-01
    Print ISSN: 1386-1425
    Electronic ISSN: 1873-3557
    Topics: Chemistry and Pharmacology , Physics
    Published by Elsevier
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  • 10
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