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  • 1
    Digitale Medien
    Digitale Medien
    Anharmonic force field and vibrational frequencies of tetrafluoromethane (CF4) and tetrafluorosilane (SiF4) (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1353-1366 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Accurate quartic anharmonic force fields for CF4 and SiF4 have been calculated using the CCSD(T) method and basis sets of spdf quality. Based on the ab initio force field with a minor empirical adjustment, the vibrational energy levels of these two molecules and their isotopomers are calculated by means of high order Canonical Van Vleck Perturbation Theory (CVPT) based on curvilinear coordinates. The calculated energies agree very well with the experimental data. The full quadratic force field of CF4 is further refined to the experimental data. The symmetrization of the Cartesian basis for arbitrary combination bands of Td group molecules is discussed using the circular promotion operator for the doubly degenerate modes, together with tabulated vector coupling coefficients. The extraction of the spectroscopic constants from our second order transformed Hamiltonian in curvilinear coordinates is discussed, and compared to a similar procedure in rectilinear coordinates. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.481590
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  • 2
    Digitale Medien
    Digitale Medien
    A nine-dimensional perturbative treatment of the vibrations of methane and its isotopomers (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 4510-4522 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The vibrations of methane isotopomers with Td, C3v, and C2v symmetry are studied by means of high order Van Vleck perturbation theory. The vibrational states up to 9000 cm−1 are investigated by combining the ab initio force field of Lee, Martin and Taylor [J. Chem. Phys. 95, 254 (1995)] with a fourth order perturbative treatment based on curvilinear normal coordinates. Implementation of the perturbation theory using both analytical and numerical expression of the kinetic energy operator is considered. The quadratic and select cubic and quartic force constants are refined via a nonlinear least squares fit to experimental data The fit force constants reproduce 130 experimental band centers with a root mean squares deviation of 0.70 cm−1. The choice of polyad quantum number is discussed with respect to different molecules. The convergence of the energy levels is discussed by carrying out the perturbation calculation up to eighth order. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.480271
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  • 3
    Digitale Medien
    Digitale Medien
    The ab initio calculated dipole moment surface and overtone relative intensities of CH chromophore in CHCl3 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 7484-7489 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Relative absorption intensities of the Fermi resonance polyads of isolated CH chromophore for the CHCl3 molecule were calculated with one-dimensional and two-dimensional dipole moment surfaces, which are obtained by the ab initio density functional method. The calculation showed an unusual strong absorption at the second Fermi resonance polyad, which agrees well with the experimental data. Such an intensities anomaly can be attributed to the nonlinearity of the dipole moment surface in the vicinity of the equilibrium configuration. By taking advantage of the two-dimensional dipole moment surface where both CH stretching and bending vibrations are taken into consideration, the ν1 and 2ν4 bands which constitute the first Fermi resonance polyad and have little wave function mixture, are found to be of almost equal intensity. Such a calculation agrees with observations. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.481346
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  • 4
    Digitale Medien
    Digitale Medien
    A nine-dimensional high order perturbative study of the vibration of silane and its isotopomers (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 5384-5400 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The vibrations of silane isotopomers with Td, C3v, and C2v symmetry are studied by means of high order canonical Van Vleck perturbation theory (CVPT). Transforming the quartic ab initio force field of Martin, Baldridge, and Lee [Mol. Phys. 95, 254 (1999)] into curvilinear normal coordinates, CVPT is used to calculate energies that agree well with experimental data. Both low energy stretch–bend combination bands and high energy stretch local mode bands of silane up to 12 000 cm−1 are well reproduced. The choice of polyad quantum number is discussed with respect to different molecules. Comparing sixth- to eighth-order level of theory, most of the levels agree to within 0.1 cm−1. Spectroscopic constants are given for all the major isotopomers. The construction of the full cubic and quartic resonance operators for symmetric top species are summarized. The Si–H and Si–D stretch modes of Td and C3v symmetry species are studied with a 4D stretch variational model using both the fitted three-parameter potential and the quartic ab initio stretch potential. Large energy level differences between these two calculations indicate that the fitted potential constants of the stretch variational model are different from those derived directly from the ab initio surface. By comparing with the nine-dimensional CVPT calculation, it is shown that the direct and indirect Fermi resonances are responsible for the inability of the four-dimensional model to fit some stretch levels. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1290027
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  • 5
    Digitale Medien
    Digitale Medien
    Vibration–rotational spectroscopy of XH2 and XH3 type molecules near the local mode limit (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 8011-8019 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Present work studies the effective rotational Hamiltonians and their vibration–rotational parameters for XH2 and XH3 type molecules near the local mode limit by including the diagonal matrix elements of coordinate operators when the bond anharmonicity is significant. An improved "α relation'' is given for the local mode limit by taking the anharmonic bond oscillator wave function as the basis function. Then the rotational tunneling approach is extended to model the effect of nonzero interbond coupling for XH2 and XH3 type molecules, which provides a dynamical view of the rovibrational structure of the local mode states. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.472714
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  • 6
    Digitale Medien
    Digitale Medien
    High resolution spectroscopic study of arsine: 3ν1 and 2ν1+ν3 dyad: The tendency of symmetry reduction (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 7310-7315 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The high resolution spectrum of AsH3 3ν1 and 2ν1+ν3 stretching overtone dyad was recorded and analyzed. The major vibration-rotation parameters of these overtones were obtained. The result indicates that these overtone vibrational states are close to the local mode limit and the rotational levels show the tendency to approach an asymmetric top. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.472590
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  • 7
    Digitale Medien
    Digitale Medien
    Six-dimensional variational calculation of the bending energy levels of HF trimer and DF trimer (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 9781-9796 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The bending energy levels of HF and DF trimer were calculated variationally using a six-dimensional kinetic-energy operator derived by constraining the stretch degrees of freedom to their equilibrium values. A basis of direct products of spherical harmonics is used to represent the wave function. The symmetry adapted Lanczos method is used to calculate levels of all symmetries from one sequence of matrix-vector products. Two efficient ways of implementing the symmetry-adapted Lanczos method are presented. To determine the concerted hydrogen bond breaking tunneling splitting in HF and DF trimer one needs to use the D3h point group. By doing D3h calculations, we find that the splitting is negligible for the low-lying levels. If the tunneling is unfeasible, the appropriate group is C3h. Our calculation using the most accurate SO-3+HF3BG potential developed by Quack, Stohner, and Suhm indicates that two gas-phase overtone bending bands of HF trimer should be reassigned, and that the noble gas matrix spectra of the bending fundamental bands are significantly shifted from their gas-phase counterparts. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1407277
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  • 8
    Digitale Medien
    Digitale Medien
    A symmetry-adapted Lanczos method for calculating energy levels with different symmetries from a single set of iterations (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 1473-1477 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We present a symmetry-adapted Lanczos method that uses projection operators to calculate energy levels with different symmetries from a single sequence of matrix–vector products. Compared with the conventional Lanczos method, this method has the advantage that energy levels are computed more efficiently and with symmetry labels. High-lying stretching energy levels of a coupled Morse oscillator Hamiltonian describing 28SiH4 are calculated to demonstrate the advantage of the symmetry-adapted method. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1331357
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  • 9
    Digitale Medien
    Digitale Medien
    Adhesion of Copper and Alumina from First Principles (2003)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 86 (2003), S. 0 
    Details
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: Structures and energetics of various, plausible realizations of the Al2O3(0001)/Cu(111) interface have been studied by density-functional theory. The oxygen-terminated interface is found to be relatively strong with a work of separation (Wsep) of 7.03 J/m2. For hydrogen-rich (e.g., moist) conditions, we have determined that the interface accommodates about 1/3 of a monolayer of hydrogen. This lowers Wsep to 4.72 J/m2, which is, however, greater than the corresponding value for bulk copper, which implies that fracture in such a system occurs in the copper region, consistent with fracture toughness experiments. We also have studied the initial stages of copper and aluminum growth on the hydrogen-stabilized oxygen-terminated Al2O3(0001) surface. Although a monolayer of aluminum already completely dissociates the interfacial O-H group, a monolayer of copper leaves it intact. If, for a thick copper film, such a full hydrogen layer were maintained, the resulting metastable interface would be very weak, with Wsep= 0.63 J/m2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03359.x
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  • 10
    Digitale Medien
    Digitale Medien
    A simple method for deriving kinetic energy operators (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 7097-7101 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We derive a general two-vector-embedded ro-vibrational kinetic energy operator (KEO) for a molecule with N atoms. Our KEO is valid for any molecule-fixed axis system attached to the two embedding vectors and any vibrational coordinates for the two-vector part of the KEO. It can be used to build up KEOs for larger molecules from KEOs for smaller molecules. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1313544
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