### Abstract

At long enough times, the idiosyncratic motions of individual solvent molecules have long since ceased to matter to the process of solvation; the fact that a real solvent is not a featureless continuum just has no bearing on the dynamics. However, at short times, typically times well under a picosecond, the situation is quite different. We show here that at least within the realm of classical mechanics, one can indeed talk about how specific molecular motions contribute to short-time solvation. Precisely how one should think about these motions depends on just how short a time interval one is considering. At the very shortest times, we use the fact that it is possible to express solvation time correlation functions rigorously as power series in time to confirm that the onset of solvation is unequivocally a matter of inertial (free-streaming) motion of individual solvent molecules. We allow for somewhat longer, but still short, time intervals by writing these same correlation functions in terms of the instanteous normal modes of the solvent. The instantaneous-normal-mode expressions allow us to decompose the solvent dynamics into separate, well-defined collective motions, each with its own characteristic abilities to foster solvation. As distinctive as they appear, these two complimentary short-time views are, in fact, equally correct in the inertial regime, a point we establish by proving that two are simply different mathematical representations of the same underlying behavior.

Original language | English |
---|---|

Pages (from-to) | 6700-6708 |

Number of pages | 9 |

Journal | The Journal of Chemical Physics |

Volume | 100 |

Issue number | 9 |

Publication status | Published - 1994 Dec 1 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics

### Cite this

*The Journal of Chemical Physics*,

*100*(9), 6700-6708.

**The short-time dynamics of solvation.** / Stratt, Richard M.; Cho, Minhaeng.

Research output: Contribution to journal › Article

*The Journal of Chemical Physics*, vol. 100, no. 9, pp. 6700-6708.

}

TY - JOUR

T1 - The short-time dynamics of solvation

AU - Stratt, Richard M.

AU - Cho, Minhaeng

PY - 1994/12/1

Y1 - 1994/12/1

N2 - At long enough times, the idiosyncratic motions of individual solvent molecules have long since ceased to matter to the process of solvation; the fact that a real solvent is not a featureless continuum just has no bearing on the dynamics. However, at short times, typically times well under a picosecond, the situation is quite different. We show here that at least within the realm of classical mechanics, one can indeed talk about how specific molecular motions contribute to short-time solvation. Precisely how one should think about these motions depends on just how short a time interval one is considering. At the very shortest times, we use the fact that it is possible to express solvation time correlation functions rigorously as power series in time to confirm that the onset of solvation is unequivocally a matter of inertial (free-streaming) motion of individual solvent molecules. We allow for somewhat longer, but still short, time intervals by writing these same correlation functions in terms of the instanteous normal modes of the solvent. The instantaneous-normal-mode expressions allow us to decompose the solvent dynamics into separate, well-defined collective motions, each with its own characteristic abilities to foster solvation. As distinctive as they appear, these two complimentary short-time views are, in fact, equally correct in the inertial regime, a point we establish by proving that two are simply different mathematical representations of the same underlying behavior.

AB - At long enough times, the idiosyncratic motions of individual solvent molecules have long since ceased to matter to the process of solvation; the fact that a real solvent is not a featureless continuum just has no bearing on the dynamics. However, at short times, typically times well under a picosecond, the situation is quite different. We show here that at least within the realm of classical mechanics, one can indeed talk about how specific molecular motions contribute to short-time solvation. Precisely how one should think about these motions depends on just how short a time interval one is considering. At the very shortest times, we use the fact that it is possible to express solvation time correlation functions rigorously as power series in time to confirm that the onset of solvation is unequivocally a matter of inertial (free-streaming) motion of individual solvent molecules. We allow for somewhat longer, but still short, time intervals by writing these same correlation functions in terms of the instanteous normal modes of the solvent. The instantaneous-normal-mode expressions allow us to decompose the solvent dynamics into separate, well-defined collective motions, each with its own characteristic abilities to foster solvation. As distinctive as they appear, these two complimentary short-time views are, in fact, equally correct in the inertial regime, a point we establish by proving that two are simply different mathematical representations of the same underlying behavior.

UR - http://www.scopus.com/inward/record.url?scp=36449002318&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=36449002318&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:36449002318

VL - 100

SP - 6700

EP - 6708

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 9

ER -