ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1
    Electronic Resource
    Electronic Resource
    Applications of the generator coordinate approximation to diatomic systems. III. Curve-crossing problems (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8945-8953 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The generator coordinate approximation, previously applied to vibration–rotation levels near potential-energy minima, is now worked out for curve-crossing situations. We define the weak and strong adiabatic coupling limits. For weak adiabatic coupling both the adiabatic and generator coordinate approximations become exact. In the strong adiabatic coupling limit the adiabatic approximation breaks down, whereas the generator coordinate approximation again reproduces the exact solutions. These theoretical results are confirmed by calculations for a Hamiltonian modeled to the EF,GK 1Σ+g curve crossing in the electronic spectrum of the hydrogen molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459233
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Generalized Tamm–Dancoff approximation (GTDA) and random-phase approximation (GRPA) calculations on LiH, Be, and Li2 (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4523-4530 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The theory for polarization propagator calculations based on a correlated reference state in the form of a spin singlet restricted antisymmetrized geminal power (AGP) is discussed. Particular attention is paid to the calculation of excitation energies and transition moments for the molecules over all internuclear separations, i.e., not just single point vertical energies, which is done in standard RPA or in higher-order treatments using perturbation methods. Simple applications to the Be atom, and the LiH and Li2 molecules are used to illustrate how this simple correlated state, which is completely determined by the choice of orbital basis (i.e., no choice of configurations is necessary), can cure the notorious consistency problems and the instabilities against the breaking of symmetry, which plague standard RPA based on a Hartree–Fock (HF) single determinantal reference state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452728
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Applications of the generator coordinate approximation to diatomic systems. II. Dunham analysis of vibration–rotation spectra (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 6352-6359 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It is shown how a Dunham series can be derived within the generator coordinate approximation. General kernel expansions are combined with order by order angular momentum projection and generator coordinate perturbation theory. The comparison of Born–Oppenheimer and generator coordinate kernal coefficients yields a clear identification of nonadiabatic effects incorporated in the generator coordinate approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452421
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Erratum: Applications of the generator coordinate approximation to diatomic systems. I. The hydrogen molecular ion [J. Chem. Phys. 84, 3944 (1986)] (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 3138-3138 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451865
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Coherent state formulation of multiconfiguration states (1991)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 1166-1175 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The theory of vector coherent states is applied to multiconfiguration states that are given a complex parametrization, based on the underlying special linear group. Using the time-dependent variational principle, equations of motion for such states are formulated as evolution equations in a generalized phase space. The classical Hamiltonian for these equations is given in terms of the reduced first- and second-order density matrices, which can be expressed in terms of partial derivatives with respect to the group parameters of the overlap kernel. The multiconfiguration self-consistent-field (MCSCF) and configuration interaction (CI) equations arise as special cases of these equations. Using the coherent state formulation we obtain very compact and numerically efficient expressions for the time-dependent quantum mechanical description of chemical reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.529313
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Trajectory and molecular binding effects in stopping cross section for hydrogen beams on H2 (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 2783-2793 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The complex interaction of an atomic projectile with a molecular target is studied by considering the time-dependent electron-nuclear dynamics of the collision. We calculate the energy loss, charge exchange, and differential cross section for a hydrogen beam colliding with molecular hydrogen targets for projectiles energies from 10 eV/amu up to 25 keV/amu. We obtain the total, electronic, nuclear, and rovibrational contribution for the orientationally averaged stopping cross section of the molecular target when scattering over all the angles is considered. We emphasize the violation of Bragg's rule (additivity of the atomic energy loss for the compound target) and the acceptance angle dependence of the experimental stopping cross section. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1436107
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Dynamics of proton-acetylene collisions at 30 eV (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 1103-1108 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Collisions of protons with ground state acetylene molecules at 30 eV are studied using the electron nuclear dynamics (END) theory. This time-dependent methodology for the study of molecular processes is a nonadiabatic approach to direct dynamics, which has been successfully applied to ion–atom and ion–molecule reactive collisions. Using the minimal END theory, we calculate the direct and charge-transfer differential cross sections. Different initial conditions lead to diverse product channels, such as charge transfer, proton exchange, and collision induced dissociation. Projectile energy loss is analyzed in terms of transfer into target electronic, translational, and rovibrational excitations. The comparison of the computed results with time-of-flight measurements is discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1485726
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Coherent state approach to electron nuclear dynamics with an antisymmetrized geminal power state (1994)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 35 (1994), S. 1139-1170 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A formulation of the complete dynamics of electrons and nuclei is presented. The dynamical equations are derived using the time-dependent variational principle (TDVP). The approximate electronic state vectors are antisymmetrized geminal power (AGP) states parameterized as projected coherent states, while the nuclei are treated as classical point particles. This leads to a formulation of time-dependent AGP theory that generalizes time-dependent Hartree–Fock (TDHF) theory and explicitly includes the dynamics of the nuclei. The linear approximation to the evolution equations (the classical harmonic approximation) which corresponds to a generalized random phase approximation (RPA) based on an AGP electronic reference state and which explicitly includes the dynamics of the nuclei, is studied and presented in this paper. The equations are formulated in terms of the primitive nonorthogonal electronic atomic basis thus avoiding any transformation to orthonormal molecular orbitals during the evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.530632
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Vibrations and soliton dynamics of positively charged polyacetylene chains (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 5433-5444 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio molecular dynamics simulation is performed on a small polyacetylene chain with a positive soliton defect. The dynamics is initialized by an external electric field. The collective motion of the carbon and hydrogen atoms are compared to some low frequency vibrational modes of positively charged polyacetylene chains of varying lengths having the characteristics of the soliton displacement. The soliton effective mass estimated using a variety of schemes is found to be about 10 electron masses. The static linear polarizability of singly charged polyacetylene chains of varying lengths is computed and compared with that of undoped chains. The electronic contributions to the polarizability are computed at the level of the coupled Hartree–Fock or the random phase approximation, and the vibrational contributions are estimated by invoking the double harmonic oscillator approximation. The soliton defect causes some enhancement of the electronic term, which covers 10–15 carbon–carbon double bonds, and it generates a large increase of the vibrational part, which in the absence of counter ions show no sign of leveling off even for the longest chains considered.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474249
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Electron nuclear dynamics of proton collisions with methane at 30 eV (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 6146-6155 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reactive collisions of protons with methane molecules at 30 eV in the laboratory frame are studied with the electron nuclear dynamics (END). The results from this theoretical approach, which does not invoke the Born–Oppenheimer approximation and does not impose any constraints on the nuclear dynamics, are compared to the results from time-of-flight measurements. Total differential cross sections and integral cross sections as well as fragmentation ratios and energy loss spectra are discussed.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474343
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...