Quantum decoherence and the isotope effect in condensed phase nonadiabatic molecular dynamics simulations

Journal of Chemical Physics

Volumn 104, Issue 15, 1996, Pages 5942-5955

  Schwartz, Benjamin J ^a,b   Bittner, Eric R ^a   Prezhdo, Oleg V ^a   Rossky, Peter J ^a  

^a UNIVERSITY OF TEXAS AT AUSTIN   (United States)

^b UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ALGORITHMS; APPROXIMATION THEORY; CHARGE TRANSFER; CHEMICAL REACTIONS; COMPUTER SIMULATION; ELECTRONS; HEAVY WATER; ISOTOPES; MOLECULAR DYNAMICS; PERTURBATION TECHNIQUES; WATER;

ELECTRON TRANSFER; HAMILTONIAN; ISOTOPE EFFECT; NONADIABATIC TRANSITIONS; NUCLEAR WAVEFUNCTION; QUANTUM DECOHERENCE; STATIONARY PHASE SURFACE HOPPING METHOD; TULLYS FEWEST SWITCHES METHOD;

QUANTUM THEORY;

EID: 0030126484     PISSN: 00219606     EISSN: None     Source Type: Journal    
DOI: 10.1063/1.471326     Document Type: Article

References (26)

1. The literature on mixed-quantum classical molecular dynamics simulations is enormous. We cite only a few recent examples here: A. Staib, D. Borgis, and J. T. Hynes, J. Chem. Phys. 102, 2487 (1995);
2. J. M. Papanikolas, P. E. Maslen, and R. Parson, J. Chem. Phys. ibid. 102, 2452 (1995);
3. Some recently developed adiabatic methods include: D. Thirumalai, E. J. Bruskin and B. J. Berne, J. Chem. Phys. 83, 230 (1985);
4. A. Selloni, R. Car, M. Parinello, and P. Carnevali, J. Phys. Chem. 91, 4947 (1987);
5. M. Sprik and M. L. Klein, J. Chem. Phys. 89, 1592 (1988).
6. There has also been a great deal of discussion of nonadiabatic dynamical algorithms and their importance to chemical reaction dynamics in the literature, which we make no attempt to review here. See, for example, the review by D. F. Coker, in Computer Simulations in Chemical Physics, edited by M. P. Allen and D. J. Tildesley (Kluwer Academic, Dordrecht, 1993), p. 315 and references therein.
7. For a few recent examples of nonadiabatic dynamical calculations, see S. Hammes-Schiffer and J. C. Tully, J. Phys. Chem. 99, 5793 (1995);
8. L. Xiao and D. F. Coker, J. Chem. Phys. 102, 1107 (1995) as well as Refs. 22-24.
9. For a discussion of quantum coherence and adiabaticity in the condensed phase, see, for example, P. G. Wolynes, J. Chem. Phys. 86, 1957 (1987).
10. We note that the quantum decoherence time presented here is not trivially related to the spectroscopic dephasing time, which is generally taken to be a measure of the fluctuations in the energy gap of the quantum system. However, we note that the two quantities are rigorously identical in the limit when the quantum system is coupled linearly to a harmonic bath. For more details on electronic dephasing in the hydrated electron system, see S. J. Rosenthal, B. J. Schwartz, and P. J. Rossky, Chem. Phys. Lett. 229, 443 (1994).
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26. If there is not enough energy available in the classical coordinates along the nonadiabatic coupling vector to make up for the change in electronic energy, the transition is rejected. As pointed out in Ref. 8, near threshold for a transition, this "rejection" feature of the algorithm leads to a branching ratio between trajectories which does not accurately reflect the corresponding diagonal elements of the density matrix. 19 It is worth noting that the classical motions along the nonadiabatic coupling vector both provide the coupling that causes the nonadiabatic transition and provide or accept the energy for the quantum transition to take place. Thus there is no formal difference between "accepting" modes and "promoting" modes in nonadiabatic dynamics.