Short time dynamics of glass-forming liquids

Roland, C. M.; Ngai, K. L.
July 1995
Journal of Chemical Physics;7/15/1995, Vol. 103 Issue 3, p1152
Academic Journal
Calculations have been presented for the intermediate scattering function, dynamic structure factor, and dynamic susceptibility of a complex correlated system undergoing relaxation with independent vibrations. The vibrational contribution was approximated by a Debye spectrum, smoothed at high frequency, while the coupling model was used to describe the relaxation. This model asserts for nonpolymeric glass-forming liquids a crossover at a microscopic time from intermolecularly uncorrelated relaxation at a constant rate to intermolecularly coupled relaxation with a time-dependent, slowed-down rate. Although the model has previously been employed to successfully predict and otherwise account for a number of macroscopic relaxation phenomena, critical phenomena are not included in, and cannot be addressed by, the coupling model. Notwithstanding an absence of any change in transport mechanism for the supercooled liquid at a critical temperature, the coupling model data, when analyzed in the manner used for mode coupling theory, shows various features interpreted by MCT as critical dynamic singularities. These include an apparent fast ‘‘β’’ relaxation giving rise to a cusp in the temperature dependence of the Debye–Waller factor, a power-law divergence in the temperature dependence of the relaxation time for the α process, and critical exponents for the relaxation having a defined relationship to one another. Additionally, other experimental features of the short-time dynamics, such as the anomalous Debye–Waller factor and the von Schweidler law, are also observed in results derived from the coupling model. Whatever similarities underlie the coupling model and MCT, a crucial difference is that only the latter predicts the existence of critical phenomena. Yet these and other distinct features are exhibited by the coupling model data. Evidently, any interpretation of short-time behavior in terms of MCT is ambiguous, if...


Related Articles

  • Molecular dynamics simulations of the glass former ortho-terphenyl. Kudchadkar, S. R.; Wiest, J. M. // Journal of Chemical Physics;11/15/1995, Vol. 103 Issue 19, p8566 

    An 18-site, three-ring model has been developed for the van der Waals system ortho-terphenyl (OTP) which has been studied extensively experimentally because of its glass forming ability. The method of constraints has been used to freeze out the fast internal modes of the molecule, but the model...

  • Vibrational predissociation of He–I2*(v)–Ne: An approximate quantal study. Villarreal, Pablo; Varade, Andrés; Delgado-Barrio, Gerardo // Journal of Chemical Physics;3/1/1989, Vol. 90 Issue 5, p2684 

    The vibrational predissociation (VP) of the He–I2(B 3Π0+u,v)–Ne complex is studied in the range of initial vibrational excitations 25≤v≤35. The rare gas atoms are restricted to move on a perpendicular plane to the I2 axis. A simple addition of pairwise Morse...

  • Experimental study of the nature of the glass transition process in monohydroxy alcohols. Murthy, S. S. N.; Nayak, S. K. // Journal of Chemical Physics;10/1/1993, Vol. 99 Issue 7, p5362 

    The nature of the glass transition process in six monohydroxy alcohols, viz., the isomers of butanol, 2-propanol, and 3-methyl–1-butanol had been studied in detail using dielectric spectroscopy (frequency range 10+6–10-3 Hz) and differential scanning calorimetry (DSC). Measurements...

  • Product state distributions for the vibrational predissociation of NeCl2. Cline, Joseph I.; Sivakumar, N.; Evard, Dwight D.; Bieler, Craig R.; Reid, Brian P.; Halberstadt, Nadine; Hair, Sally R.; Janda, Kenneth C. // Journal of Chemical Physics;3/1/1989, Vol. 90 Issue 5, p2605 

    Product state distributions are reported for the vibrational predissociation of the NeCl2, B state, v’=6 through v’=13 levels. For the lower vibrational levels, Δv=-1 dissociation produces a bimodal Cl2 product rotational state distribution with the first maximum at j=4 and a...

  • Diffusion and clustering of N[sub 2]O molecules in argon clusters: A theoretical approach by... Gaigeot, M.-P.; de Pujo, P. // Journal of Chemical Physics;6/8/1997, Vol. 106 Issue 22, p9155 

    Presents results of molecular dynamics simulations of small van der Waals clusters composed of one argon cluster of size 147 or 125 and from one to four nitrous oxide (N [sub 2]O) molecules deposited at thermal relative collision energy on the argon cluster. Necessity and practical application...

  • Real-time dynamics of clusters. II. I2Xn (n=1; X=He, Ne, and H2), picosecond fragmentation. Gutmann, M.; Willberg, D. M.; Zewail, A. H. // Journal of Chemical Physics;12/1/1992, Vol. 97 Issue 11, p8037 

    In this second paper (II) of a series, we report our picosecond time-resolved studies of the state-to-state rates of vibrational predissociation in iodine–rare gas (van der Waals) clusters. Particular focus is on the simplest system, I2He, which serves as a benchmark for theoretical...

  • Efficient multiple-time-step integrators with distance-based force splitting for particle-mesh-Ewald molecular dynamics simulations. Qian, Xiaoliang; Schlick, Tamar // Journal of Chemical Physics;4/8/2002, Vol. 116 Issue 14, p5971 

    We develop an efficient multiple-time-step force splitting scheme for particle-mesh-Ewald molecular dynamics simulations. Our method exploits smooth switch functions effectively to regulate direct and reciprocal space terms for the electrostatic interactions. The reciprocal term with the near...

  • A supertensor formalism for solute–continuum solvent interactions with an arbitrarily shaped cavity. I. Theory and implementation. Drummond, Malcolm L. J. // Journal of Chemical Physics;4/15/1988, Vol. 88 Issue 8, p5014 

    A polarizable molecule is allowed to interact with its surroundings, represented by a dielectric continuum. The molecule lies in a cavity which is its van der Waals envelope. The supertensor formulation of many-body electrostatics is invoked to enable a consistent solution to be found. A...

  • The heat flux vector for highly inhomogeneous nonequilibrium fluids in very narrow pores. Todd, B. D.; Evans, Denis J. // Journal of Chemical Physics;12/8/1995, Vol. 103 Issue 22, p9804 

    In this paper we present the results of nonequilibrium molecular dynamics simulations of an atomic fluid undergoing planar Poiseuille flow through a narrow slit pore. In particular we examine the heat flux vector for such a fluid and find that it displays weak oscillations with wavelengths that...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics