GLORIA

GEOMAR Library Ocean Research Information Access

Your search history is empty.
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
Document type
Years
  • 1
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The expressions for vibrational energy relaxation (VER) rates of polyatomic molecules in terms of equilibrium capacity time correlation functions (TCFs) derived in the first paper of this series [J. Chem. Phys. 110, 5273 (1999)] are used for the investigation of VER of azulene in carbon dioxide at low (3.2 MPa) and high (270 MPa) pressure. It is shown that for both cases the VER times evaluated on the basis of the same potential model via solute–solvent interaction capacity TCFs by means of equilibrium molecular dynamics (EMD) simulations satisfactorily agree with the nonequilibrium (NEMD) molecular dynamics [J. Chem. Phys. 110, 5286 (1999)] and experimental [J. Chem. Phys. 105, 3121 (1996)] results as well. Thus it follows that these methods can complement each other in characterizing VER from different points of view. Although more computational power and refined methods of dealing with simulated data are required for EMD simulations, they allow the use of powerful tools of equilibrium statistical mechanics for investigating the relaxation process. To this end, an analysis of VER mechanisms on the basis of normal mode and atomic representations is carried out. The influence of temperature and CO2 pressure on azulene normal mode spectra and solvent assisted intermode coupling in connection with the eigenvector structure is investigated in great detail. The normal mode capacity cross-correlation matrix reveals the significance of intermode coupling, which significantly contributes to intramolecular vibrational energy redistribution (IVR). As a new concept, partial normal mode relaxation rates are introduced. It is shown that these rates demonstrate similar properties as the energy exchange rates through particular normal modes in nonequilibrium simulations. Atomic spectra and friction coefficients are characterized by a complicated frequency dependence due to contributions from many normal modes. Atomic capacity TCFs and partial relaxation rates are analyzed and reveal a similar picture to that obtained from NEMD simulations. These results show that VER and IVR cannot be separated from each other and have to be considered as mutually connected processes. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 5273-5285 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Methods of implementation of classical molecular dynamics simulations of moderate size molecule vibrational energy relaxation and analysis of their results are proposed. Two different approaches are considered. The first is concerned with modeling a real nonequilibrium cooling process for the excited molecule in a solvent initially at equilibrium. In addition to the solute total, kinetic, and potential energy evolution, that define the character of the process and the rate constant or relaxation time, a great deal of important information is provided by a normal mode specific analysis of the process. Expressions for the decay of the normal mode energies, the work done by particular modes, and the vibration–rotation interaction are presented. The second approach is based on a simulation of a solute–solvent system under equilibrium conditions. In the framework of linear nonequilibrium statistical thermodynamics and normal mode representation of the solute several expressions for the rate constant are derived. In initial form, they are represented by integrals of the time correlation functions of the capacities of the solute–solvent interaction atomic or normal mode forces and include the solute heat capacity. After some approximations, which are adequate for specific cases, these expressions are transformed to combinations of those for individual oscillators with force–force time correlation functions. As an attempt to consider a strongly nonequilibrium situation we consider a two-temperature model and discuss the reason why the rate constant can be independent on the solute energy or temperature. Expressions for investigation of the energy redistribution in the solvent are derived in two forms. One of them is given in the usual form of a heat transfer equation with the source term describing the energy flux from the excited solute. The other form describes the energy redistribution in the solvent in terms of capacity time correlation functions and can be more convenient if memory effects and spatial dispersion play an important role in energy redistribution in the solvent. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 5286-5299 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results of nonequilibrium molecular dynamics simulations of vibrational energy relaxation of azulene in carbon dioxide and xenon at low and high pressure are presented and analyzed. Simulated relaxation times are in good agreement with experimental data for all systems considered. The contribution of vibration–rotation coupling to vibrational energy relaxation is shown to be negligible. A normal mode analysis of solute-to-solvent energy flux reveals an important role of high-frequency modes in the process of vibrational energy relaxation. Under all thermodynamic conditions considered they take part in solvent-assisted intramolecular energy redistribution and, moreover, at high pressure they considerably contribute to azulene-to-carbon dioxide energy flux. Solvent-assisted (or collision-induced) intermode energy exchange seems to be the main channel, ensuring fast intramolecular energy redistribution. For isolated azulene intramolecular energy redistribution is characterized by time scales from several to hundreds of ps and even longer, depending on initial excitation. The major part of solute vibrational energy is transferred to the solvent via solute out-of-plane vibrational modes. In-plane vibrational modes are of minor importance in this process. However, their contribution grows with solvent density. The distribution of energy fluxes via azulene normal modes strongly depends on thermodynamic conditions. The contribution of hydrogen atoms to the overall solute-to-solvent energy flux is approximately two to three times higher than of carbon atoms depending on the system and thermodynamic conditions as well. Carbon atoms transfer energy only in the direction perpendicular to the molecular plane of azulene, whereas hydrogen atoms show more isotropic behavior, especially at high pressure. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1090-6525
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A simple and effective self-consistent scheme is proposed for the determination of the average potentials which allows thermodynamic functions and other characteristics of lattice systems in equilibrium to be calculated with high accuracy and short computing time. This scheme has been used for analysis of the expressions for the coefficients of diffusion and electrical conductivity obtained on the basis of the modern statistical theory of nonequilibrium processes. Results of the simulations are correlated with the data of Monte Carlo simulations obtained using parallel vector algorithms on a Cray TZE computer of the Max Plank Society (Germany).
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering physics and thermophysics 68 (1995), S. 599-604 
    ISSN: 1573-871X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Within the framework of the Enskog theory expressions are obtained for the tensors of the friction and self-diffusion coefficients in the ordered nematic phase of a system of nonspherical particles. Calculations of the tensor of the self-diffusion coefficients are performed; their comparison with the data of a computer experiment shows that the Enskog theory can be used to calculate the kinetic coefficients in such systems up to densities of 0.6–0.7 of the close-packing density.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Ionics 3 (1997), S. 44-51 
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The self-diffusion coefficient for a stochastically nonuniform thermodynamic system is represented as the mean value of the transition rates. A model for the ionic transport in solid oxide electrolytes is proposed. The existence of percolation cluster of the doping cations is taken into account in the model. The maximum of the concentration dependence of the ionic conductivity is explained by the blocking effect and random distribution of traps. The problem of inconsistency of theoretical and experimental values for the pre-exponential factor is discussed and an approach is proposed to overcome this disagreement.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1573-9228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is shown that by approximating the potential of mean forces which can be used to complete a network of integrodifferential equations, as distinct from the approximation of a particle distribution function, one is able to obtain thermodynamically matched thermal and calorific state equations.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...