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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 116 (1994), S. 7266-7273 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 110 (1988), S. 2361-2368 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    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 89 (1988), S. 5695-5703 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The steady state rate constant for passage over a fluctuating potential barrier is derived from the Fokker–Planck equation using the stable states picture. The time scale of fluctuations in barrier height and position do not influence the reactive frequency; however, the reactive frequency does depend upon the time scale of fluctuations in the barrier curvature. If these are fast relative to [ω2m+(ξ/2)2]1/2, where ωm is the mean barrier frequency and ξ is the friction for motion along the reaction coordinate, then the crossing takes place on the potential of mean force. If the barrier fluctuations are slow on the same time scale, then the rate is an average over that for the distribution of barriers. In both of these limits the form of the Kramers solutions is recovered, whereas in the intermediate case, the rate also depends explicitly on the relaxation time scale of the fluctuations. A physically reasonable model for the decay of fluctuations in the potential is proposed and used to obtain an analytic expression for the rate that covers the range between these two limits.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2526-2535 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A time-local Fokker–Planck equation (TLFPE) is derived which accounts for memory effects in stochastic problems. This is expected to provide a computationally efficient method of modeling the phase space evolution of such systems by simple (local time) Langevin equations with Markovian fluctuating forces that are characterized by time-dependent moments; it is this explicit time dependence that describes the memory effects. The TLFPE is derived from the probability theory of non-Markovian systems as a generalization of Chandrasekar's derivation of the Fokker–Planck equation (FPE) from the Chapman–Kolmogarov equation for Markovian systems. In this article it is applied to free particle diffusion and barrier crossing problems, and is shown to give rise to physically realistic results. Further, the form of the TLFPE suggests that the conditions required for systems to exhibit Markovian behavior are less restrictive than the Brownian criterion of separation of time scales between the fluctuating forces and the momentum response of the system. Rather, a sufficient condition is that the time-dependent moments of the TLFPE reach plateau values before the time scale of the phenomenon of interest.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2446-2447 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The undamped modes found by Diestler and Riley [J. Chem. Phys. 83, 3584 (1985)] to arise in Brownian lattice dynamics are shown to be a real, though unobservable, consequence of the consideration of a zero frequency limit. As a result, it is shown that dissipative processes (such as those described by Brownian motion theory) need to be considered to arise as a "plateau'' behavior of a system at long times (or small frequencies), and not as an infinite time (zero frequency) limit.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 6448-6458 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular dynamics simulations are reported for a solute immersed in a monatomic solvent; systems modeled represent monatomic and diatomic solute species (whose atoms are larger and heavier than the solvent), with varying force constant and bond length for the diatomic. From these simulations, autocorrelation functions, diffusion coefficients (D), and friction coefficients (ξ) are determined; for the diatomic, these are found for both the center-of-mass and relative coordinates. These results are used to develop simple models for D and ξ, including (for the diatomic relative coordinate) their frequency dependence. The models enable D and ξ to be readily determined from properties such as bulk viscosity, potential parameters, etc. These D and ξ can be used to interpret and predict picosecond time scale data for solute dynamics using stochastic models (e.g., the Kramers or Langevin equations) at the molecular level; their theoretical basis is such that they should apply to many types of solute moieties (e.g., aromatic rings) as well as to the large atoms used in the simulations.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 6850-6855 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 94 (1990), S. 6080-6089 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 3358-3362 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The N-particle Fokker–Planck equation has been cast into a form which is invariant to coordinate transformations. For a pair of particles interacting through a radial potential V(R), the equation of motion may be projected onto a one-dimensional problem in R when the conjugate momenta of the center of mass and internal coordinates have symmetric distributions, as in Boltzmann distributions. However, the R2 dependence of the density of configuration space demands that V(R) be supplemented with an effective repulsive potential −2kT ln R, a result which has consequences for Langevin simulations of chemical processes. For N interacting particles a subset of coordinates can often be identified as having such symmetric distributions, and if these are not of interest, they can be eliminated with the result that the potential containing the remaining coordinates is supplemented by −kT ln(||gkl||)1/2, where ||gkl|| is the determinant of that portion of the covariant metric tensor pertaining to unwanted coordinates k and l.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 363-367 
    ISSN: 0192-8651
    Keywords: solution structuring ; radial distribution functions ; available volume ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The traditional method of analyzing solution structuring properties of solutes using atom-atom radial distribution functions (rdfs) can give rise to misleading interpretations when the volume occupied by the solute is ignored. It is shown by using the examples of O(4) in α- and β-D-allose that a more reliable interpretation of rdfs can be obtained by normalising the rdf using the available volume, rather than the traditional volume of a spherical shell.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 363-367, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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