Instantaneous normal mode analysis of binary liquid ArKr mixtures

Stassen, Hubert; Gburski, Z.

doi:10.1016/0009-2614(93)e1390-3

Cited by 27 publications

(4 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One immediate consequence is that we can predict the densities of states well enough to explore some of the solution phenomenology just alluded to. We find that we can understand much of this behavior with a one-fluid mixture theory that not only explains the observations of Stassen and Gburski, 9 but predicts other invariances as well. Furthermore, we find that our theory is flexible enough to compute single-species projections of the density of states analytically.…”

Section: Introductionsupporting

confidence: 60%

Liquid theory for the instantaneous normal modes of a liquid. II. Solutions

Larsen

Goodyear

Stratt

1996

The Journal of Chemical Physics

View full text Add to dashboard Cite

The molecular origins of the two-dimensional Raman spectrum of an atomic liquid. II. Instantaneous-normalmode theory There are a number of different ways of thinking about the intermolecular vibrations present in liquids. The approach suggested by instantaneous normal modes is a particularly interesting one, not just because of its connections with short-time dynamics, but because these modes can be analyzed and computed using the statistical mechanical ideas of standard liquid theory-or at least they can for neat, atomic liquids. We show in this paper that the instantaneous normal modes of atomic mixtures can be handled in virtually an identical fashion. We construct a renormalized mean-field theory that allows us to predict not only the total density of states of the mixture's instantaneous normal modes, but also its projections into species-specific parts. This projection then allows us to predict the separate dynamics of all the species present in the mixture. We illustrate these results by applying them first to mixtures of Ar and Kr and then to binary isotopic mixtures with far more extreme mass differences, comparing in both cases with simulation. For mixtures of atoms not much more disparate than Ar and Kr, we find that the solution densities of states can be described quantitatively, over the entire range of compositions, merely by regarding the system as an effective neat liquid in appropriately scaled units. When the masses of the components differ by an order of magnitude or more, this simple scaling no longer holds, but what is interesting is that the liquid's behavior is also quite different from what one would have seen in substitutionally disordered crystals with this same mass ratio. The dynamics of a light solute in a liquid makes an especially sharp contrast with that of an analogous light impurity in a crystal lattice.

show abstract

Section: Introductionsupporting

confidence: 60%

Liquid theory for the instantaneous normal modes of a liquid. II. Solutions

Larsen

Goodyear

Stratt

1996

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…The instantaneous normal modes,9 [30][31][32][33][34][35][36][37][38][39][40][41] for better or worse, differ in significant ways from all of these approaches. It should be emphasized that the computational scheme for generating them has been applied from time to time for almost 20 years,42-44 but what seem to be the new features are, first, the realization that instantaneous normal modes can provide an accurate picture of the short-time dynamics of liquids at a completely microscopic level and, second, that, despite their wealth of detail, one can actually understand some of their properties from the statistical mechanics of liquids.…”

Section: What Instantaneous Normal Modes Are and Are Notmentioning

confidence: 99%

The Instantaneous Normal Modes of Liquids

Stratt¹

1995

Acc. Chem. Res.

375

259

View full text Add to dashboard Cite

“…It is not obvious how to meet this challenge in its most general sense, but given the very short times pertinent to solvation, it seems plausible that an instantaneous-normal-mode description of liquids might be able to provide a reasonable starting point. That is, the fact that liquids tend to evolve as if they were governed by harmonic intermolecular vibrations, ,− at least at short times, can be used to try to capture the way in which the solute−solvent interaction energy changes with time. The ease with which this harmonic motion can be dissected into well-defined normal modes will then let us assign a specific molecular identity to the components of the solvent dynamics most active in the solvation. − …”

Section: Introductionmentioning

confidence: 99%

Short-Time Dynamics of Solvation: Relationship between Polar and Nonpolar Solvation

1996

View full text Add to dashboard Cite

The microscopic details of how a solution responds to changes in a solute are now becoming experimentally accessible at the kinds of times that should allow us to follow even the earliest events in solvation. For time scales this short there is a genuine chance that one can identify actual elementary events in the solvation process, meaning that one can begin to think about explicit solvation mechanismsthe specific molecular motions that comprise the crucial steps in the process. Most of the current theories of solvation dynamics, however, try to resolve this early-time dynamics by looking at finer and finer details of the dielectric response of the bulk solvent, an approach which not only seems to be starting from the opposite extreme of the behavior one is trying to understand, but which erects an artificial conceptual barrier between the solvation processes of polar and nonpolar liquids. We suggest that, at least at the times of interest for questions of solvation mechanism, the distinction between polar and nonpolar solvents is superficial. The ultrafast dynamics of both kinds of solvents are more naturally regarded in terms of their instantaneous normal modeswhich can be further dissected into contributions from such mechanistic elements as solvent libration and solvent translation, and even into contributions from individual solvent shells surrounding the solute, if so desired. We show how, from the perspective of this kind of analysis, a simple scaling argument makes it clear why solvent libration is usually, but not always, the most efficient route to solvationand why the important distinctions are not between the different families of solvents, but between the differing symmetries of the various solute−solvent interactions that one can choose to monitor experimentally. We illustrate these ideas by performing an instantaneous-normal-mode analysis of the manifestly nonpolar situation of I2 dissolved in liquid CO2, an example deliberately chosen to contrast with our previous study of dipolar solvation in CH3CN. In accordance with the predictions of the simple scaling argument, the primary solvation mechanism shifts from libration to center-of-mass translation as the solute−solvent interaction being monitored is changed from being multipolar in character (dipolar or quadrupolar) to something more symmetric. We find, moreover, that the range of the solute−solvent interaction is of no more than secondary importance in understanding the solvation mechanism: Coulombic (1/r) potentials behave little differently than dispersion (1/r 6) potentials in their libration/translation preferences, and both exhibit a prompt solvation process dominated by the first solvation shell. Much the same kind of analysis can be applied to the question of whether solute motion is an important part of solvation: although unfreezing the solute will always allow for faster solvent response, we show that the extent of the effect can be quantitatively predicted by comparing the solute's mass and moment of inertia with that of the sol...

show abstract

Instantaneous normal mode analysis of binary liquid ArKr mixtures

Cited by 27 publications

References 23 publications

Liquid theory for the instantaneous normal modes of a liquid. II. Solutions

Liquid theory for the instantaneous normal modes of a liquid. II. Solutions

The Instantaneous Normal Modes of Liquids

Short-Time Dynamics of Solvation: Relationship between Polar and Nonpolar Solvation

Contact Info

Product

Resources

About