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Volumn 105, Issue 22, 1996, Pages 10050-10071

The short-time intramolecular dynamics of solutes in liquids. I. An instantaneous-normal-mode theory for friction

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EID: 0001237035     PISSN: 00219606     EISSN: None     Source Type: Journal    
DOI: 10.1063/1.472835     Document Type: Article
Times cited : (58)

References (163)
  • 19
    • 85033061989 scopus 로고    scopus 로고
    • note
    • It is convenient for pedagogical purposes to refer to the tagged coordinate as that of the "solute" and the perturbing environment coupled to this coordinate as the "solvent." The reader might want to keep in mind, however, that with polyatomic solutes it is frequently useful to classify the other solute coordinates as the part of the perturbing bath felt by the tagged coordinate, and therefore as part of the "solvent."
  • 24
    • 36549091053 scopus 로고
    • Even in the low-friction regime, where energy diffusion dominates the dynamical corrections, Pollak-Grabert-Hänggi theory suggests that one needs to know no more about the dynamics of the solvent than the friction in order to be able to predict reaction rates reasonably accurately. E. Pollak, H. Grabert, and P. Hänggi, J. Chem. Phys. 91, 4073 (1989).
    • (1989) J. Chem. Phys. , vol.91 , pp. 4073
    • Pollak, E.1    Grabert, H.2    Hänggi, P.3
  • 34
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    • Chem. Phys. Lett. 240, 125 (1995).
    • (1995) Chem. Phys. Lett. , vol.240 , pp. 125
  • 42
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    • fit the friction kernel for a rare-gas liquid (obtained from an MD simulation) to a sum of an exponential and a Gaussian. For applications of this model to chemical reaction rates
    • Levesque and Verlet [D. Levesque and L. Verlet, Phys. Rev. A 2, 2514 (1970)] fit the friction kernel for a rare-gas liquid (obtained from an MD simulation) to a sum of an exponential and a Gaussian. For applications of this model to chemical reaction rates,
    • (1970) Phys. Rev. A , vol.2 , pp. 2514
    • Levesque, D.1    Verlet, L.2
  • 48
    • 85033043559 scopus 로고    scopus 로고
    • note
    • -1x(0). Here the dagger denotes a transpose, and the brackets are ensemble averages over initial conditions.
  • 49
    • 85033040852 scopus 로고    scopus 로고
    • note
    • This GLE differs from Eq. (1) in that the force from the potential of mean force has been replaced by a harmonic force subject to an effective frequency ω̄. Note that this feature follows rigorously from the derivation; in particular, it does not require that we have a genuinely harmonic solute.
  • 59
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    • J. Phys. Chem. 94, 8625 (1990);
    • (1990) J. Phys. Chem. , vol.94 , pp. 8625
  • 61
    • 85033040218 scopus 로고    scopus 로고
    • For notational simplicity we shall write the tagged coordinate as a scalar, although a vector valued coordinate is no more difficult to work with
    • For notational simplicity we shall write the tagged coordinate as a scalar, although a vector valued coordinate is no more difficult to work with.
  • 64
    • 0001285118 scopus 로고
    • Seeing the bath represented as a collection of harmonic oscillators immediately suggests that a quantum mechanical generalization could be obtained simply by quantizing the oscillators. Indeed, quantum dissipation is normally treated with this strategy. P. G. Wolynes, Phys. Rev. Lett. 47, 968 (1981);
    • (1981) Phys. Rev. Lett. , vol.47 , pp. 968
    • Wolynes, P.G.1
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    • and Progr. Theor. Phys. 153, 445(E) (1984);
    • (1984) Ann. Phys. , vol.153 , Issue.E , pp. 445
  • 71
    • 36449000069 scopus 로고
    • We shall limit ourselves here to the purely classical regime, but we do note that recent advances in formulating quantum mechanical instantaneous normal modes may very well allow us to handle quantum mechanical situations. J. Cao and G. A. Voth, J. Chem. Phys. 101, 6184 (1994);
    • (1994) J. Chem. Phys. , vol.101 , pp. 6184
    • Cao, J.1    Voth, G.A.2
  • 72
    • 85033035995 scopus 로고    scopus 로고
    • C. Chakravarty and R. Ramaswamy, (preprint); in press
    • C. Chakravarty and R. Ramaswamy, (preprint); S. A. Corcelli and J. D. Doll, Chem. Phys. Lett, (in press).
    • Chem. Phys. Lett
    • Corcelli, S.A.1    Doll, J.D.2
  • 77
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    • Phys. Rev. E 51, 1868 (1995).
    • (1995) Phys. Rev. E , vol.51 , pp. 1868
  • 81
    • 4243304121 scopus 로고
    • It is possible to include position-dependent friction by making the coupling constants functions of the tagged coordinate. Some relevant references are B. Carmeli and A. Nitzan, Chem. Phys. Lett. 102, 517 (1983);
    • (1983) Chem. Phys. Lett. , vol.102 , pp. 517
    • Carmeli, B.1    Nitzan, A.2
  • 92
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    • J. Chem. Phys. 69, 336 (1978);
    • (1978) J. Chem. Phys. , vol.69 , pp. 336
  • 96
    • 85033057579 scopus 로고    scopus 로고
    • For instance, a linear spectrum of couplings, J(ω)∝ω, corresponds to Ohmic friction [see Caldeira and Leggett, Ref. 50].
    • For instance, a linear spectrum of couplings, J(ω)∝ω, corresponds to Ohmic friction [see Caldeira and Leggett, Ref. 50].
  • 99
    • 36448999848 scopus 로고
    • J. Chem. Phys. 103, 8501 (1995).
    • (1995) J. Chem. Phys. , vol.103 , pp. 8501
  • 100
    • 0003428968 scopus 로고
    • edited by G. R. Fleming and P. Hänggi World Scientific, Singapore
    • The bath harmonic oscillators here are determined through variational transition state theory: E. Pollak, in Activated Barrier Crossing, edited by G. R. Fleming and P. Hänggi (World Scientific, Singapore, 1993);
    • (1993) Activated Barrier Crossing
    • Pollak, E.1
  • 105
    • 11744385054 scopus 로고    scopus 로고
    • J. Chem. Phys. 104, 4736 (1996);
    • (1996) J. Chem. Phys. , vol.104 , pp. 4736
  • 106
    • 5644224996 scopus 로고    scopus 로고
    • J. Phys. Chem. 100, 10355 (1996).
    • (1996) J. Phys. Chem. , vol.100 , pp. 10355
  • 112
    • 33748625353 scopus 로고    scopus 로고
    • J. Chem. Phys. 100, 1266 (1996).
    • (1996) J. Phys. Chem. , vol.100 , pp. 1266
  • 115
    • 85033040073 scopus 로고    scopus 로고
    • We assume appropriate mass-weighting here (see Ref. 73).
    • We assume appropriate mass-weighting here (see Ref. 73).
  • 116
    • 0001140409 scopus 로고    scopus 로고
    • An alternative approach to handling the imaginary modes was recently suggested: T. Keyes, J. Chem. Phys. 104, 9349 (1996).
    • (1996) J. Chem. Phys. , vol.104 , pp. 9349
    • Keyes, T.1
  • 117
    • 85033055053 scopus 로고    scopus 로고
    • In principle the tagged coordinate, x, could well be vectorial in character. For notational simplicity, however, we shall assume x is a scalar in this development.
    • In principle the tagged coordinate, x, could well be vectorial in character. For notational simplicity, however, we shall assume x is a scalar in this development.
  • 119
    • 85033071409 scopus 로고    scopus 로고
    • This step is not a trivial as it may appear. Within a site-site pair-potential representation of the potential energy, each solute-solvent pair potential will involve both intramolecular and center-of-mass coordinates.
    • This step is not a trivial as it may appear. Within a site-site pair-potential representation of the potential energy, each solute-solvent pair potential will involve both intramolecular and center-of-mass coordinates.
  • 120
    • 85033054531 scopus 로고    scopus 로고
    • note
    • If orientational degrees of freedom are included, then the "masses" will not only contain instantaneous values of the bath coordinates (see Ref. 73), but may also depend on the time-dependent tagged coordinate. This situation can arise because the bath coordinates will often include the nontagged intramolecular solute coordinates: if x were the interatomic distance in a diatomic, then because of centrifugal distortion, the bath would contain angular momentum terms with an x-dependent moment of inertia. Since the effects are small in practice, we shall ignore this last complication for the purpose of this paper.
  • 121
    • 85033046693 scopus 로고    scopus 로고
    • 0.
    • 0.
  • 122
    • 85033052227 scopus 로고    scopus 로고
    • l(ω)], and the "R" and "I" subscripts denote the real and imaginary parts of the transform, respectively.
    • l(ω)], and the "R" and "I" subscripts denote the real and imaginary parts of the transform, respectively.
  • 123
    • 85033059684 scopus 로고    scopus 로고
    • R(ω) has a delta function contribution at zero frequency - but the J(ω)'s are identical.
    • R(ω) has a delta function contribution at zero frequency - but the J(ω)'s are identical.
  • 124
    • 85033049634 scopus 로고    scopus 로고
    • note
    • eq=1.25σ and spatially fixed. Note that only configurational information, not dynamics, is used in these INM calculations.
  • 125
    • 85033062647 scopus 로고    scopus 로고
    • note
    • LJ the (Lennard-Jones) unit of time and the solvent mass, respectively]. Note also that the INM spectrum of couplings becomes complex if there are any imaginary modes in the INM spectrum. However, these imaginary modes make such a small contribution (here only 1%) to the associated influence spectrum [Eqs. (41)-(43)] that we feel justified in plotting only the real portion in this and subsequent spectrum-of-couplings figures.
  • 128
    • 85033068579 scopus 로고    scopus 로고
    • Specifically, a GLE results only if the coupling is linear in the solvent (see Ref. 49).
    • Specifically, a GLE results only if the coupling is linear in the solvent (see Ref. 49).
  • 130
    • 85033066595 scopus 로고    scopus 로고
    • An implicit assumption here is that the kinetic energy depends only on velocities, not positions. This restriction is not fundamental, but working beyond it requires specifying the particulars of the system.
    • An implicit assumption here is that the kinetic energy depends only on velocities, not positions. This restriction is not fundamental, but working beyond it requires specifying the particulars of the system.
  • 131
    • 85033041584 scopus 로고    scopus 로고
    • Insofar as the real-frequency modes are concerned, the initial configuration distribution (the one corresponding to the true potential surface) is just a nonequilibrium starting point from which the set of harmonic oscillators must relax according to their own dictates. The imaginary modes lead to unphysical behavior at long times simply because they have no stable equilibrium to reach.
    • Insofar as the real-frequency modes are concerned, the initial configuration distribution (the one corresponding to the true potential surface) is just a nonequilibrium starting point from which the set of harmonic oscillators must relax according to their own dictates. The imaginary modes lead to unphysical behavior at long times simply because they have no stable equilibrium to reach.
  • 133
    • 85033055404 scopus 로고    scopus 로고
    • max, that will capture the entire spectrum to within an arbitrarily small tolerance
    • max, that will capture the entire spectrum to within an arbitrarily small tolerance.
  • 134
    • 85033061478 scopus 로고    scopus 로고
    • note
    • 2)> [as opposed to the frequency-weighted spectrum, Eqs. (41) and (42)] will be nonzero at λ=0 as well.
  • 136
    • 85033068506 scopus 로고    scopus 로고
    • note
    • -2=∞.
  • 137
    • 85033072109 scopus 로고    scopus 로고
    • 2 [see Ref. 73].
    • 2 [see Ref. 73].
  • 138
    • 85033037464 scopus 로고    scopus 로고
    • 4 snapshots were employed to reduce the noise further.
    • 4 snapshots were employed to reduce the noise further.
  • 139
    • 1542469206 scopus 로고
    • Usually, one needs only the (configuration-averaged) friction kernel and the potential of mean force to compute correlation functions from the GLE (see Ref. 39). If detailed solute dynamics are required, however, then the GLE must be solved as a stochastic differential equation, with the fluctuating force treated as a stochastic variable. See, for example, J. D. Doll and D. R. Dion, J. Chem. Phys. 65, 3762 (1976);
    • (1976) J. Chem. Phys. , vol.65 , pp. 3762
    • Doll, J.D.1    Dion, D.R.2
  • 142
    • 85033047781 scopus 로고    scopus 로고
    • x exp(-st)f(t).
    • x exp(-st)f(t).
  • 143
    • 85033048384 scopus 로고    scopus 로고
    • Recall also that ℱ is independent of the initial velocity of the tagged coordinate.
    • Recall also that ℱ is independent of the initial velocity of the tagged coordinate.
  • 145
    • 0004158133 scopus 로고
    • Academic, New York
    • R(ω) in the numerator. Contour integration proves that the added term vanishes. See P. J. Davis and P. Rabinowitz, Methods of Numerical Integration (Academic, New York, 1975), pp. 147-150.
    • (1975) Methods of Numerical Integration , pp. 147-150
    • Davis, P.J.1    Rabinowitz, P.2
  • 146
    • 85033072203 scopus 로고    scopus 로고
    • x(ω) is just the full density of states D(ω).
    • x(ω) is just the full density of states D(ω).
  • 147
    • 85033046596 scopus 로고    scopus 로고
    • usp(ω)/2, and these are the quantities plotted as the single-particle J(ω)'s in Fig. 5.
    • usp(ω)/2, and these are the quantities plotted as the single-particle J(ω)'s in Fig. 5.
  • 151
    • 85033045282 scopus 로고    scopus 로고
    • See also Deutch and Silbey, Ref. 45.
    • See also Deutch and Silbey, Ref. 45.
  • 152
    • 85033066991 scopus 로고    scopus 로고
    • -(1/2)ω2 f t 2-1].
    • -(1/2)ω2 f t 2-1].
  • 153
    • 85033052465 scopus 로고    scopus 로고
    • The influence spectrum is, of course, invariant to changing the signs of the mode coefficients.
    • The influence spectrum is, of course, invariant to changing the signs of the mode coefficients.
  • 154
    • 85033059616 scopus 로고    scopus 로고
    • note
    • Since the fluctuating force vanishes at time 0, we cannot literally integrate Eq. (83), with A the fluctuating force, in order to obtain the GLE friction. If one could do so the INM friction would satisfy the ordinary fluctuation-dissipation relation, Eq. (2). [See Sees. III C and IV C.] Nonetheless, our derivation does indeed show that Eq. (85), the analogue of Eq. (84), is correct.
  • 159
    • 33645805902 scopus 로고
    • Dover, New York
    • by N. Wax (Dover, New York, 1954).
    • (1954)
    • Wax, N.1
  • 161
    • 36849134126 scopus 로고
    • J. Chem. Phys. 36, 2227 (1962).
    • (1962) J. Chem. Phys. , vol.36 , pp. 2227


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