TY - JOUR
T1 - Ideal glass transitions, shear modulus, activated dynamics, and yielding in fluids of nonspherical objects
AU - Yatsenko, Galina
AU - Schweizer, Kenneth S.
N1 - Funding Information:
This work was supported by the U.S. Department of Energy, Division of Material Sciences, through the Frederick Seitz Materials Research Laboratory at UIUC funded by Grant No. DEFG02-91ER45439. The authors thank Lisa Hall and Erica Saltzman for technical assistance, and Matthias Sperl for helpful comments on the manuscript.
PY - 2007
Y1 - 2007
N2 - An extension of nave ideal mode coupling theory (MCT) and its generalization to treat activated barrier hopping and glassy dynamics in fluids and suspensions composed of nonspherical hard core objects is proposed. An effective center-of-mass description is adopted. It corresponds to a specific type of preaveraging of the dynamical consequences of orientational degrees of freedom. The simplest case of particles composed of symmetry-equivalent interaction sites is considered. The theory is implemented for a homonuclear diatomic shape of variable bond length. The nave MCT glass transition boundary is predicted to be a nonmonotonic function of the length-to-width or aspect ratio and occurs at a nearly unique value of the dimensionless compressibility. The latter quantifies the amplitude of long wavelength thermal density fluctuations, thereby (empirically) suggesting a tight connection between the onset of localization and thermodynamics. Localization lengths and elastic shear moduli for different aspect ratio and volume fraction systems approximately collapse onto master curves based on a reduced volume fraction variable that quantifies the distance from the ideal glass transition. Calculations of the entropic barrier height and hopping time, maximum restoring force, and absolute yield stress and strain as a function of diatomic aspect ratio and volume fraction have been performed. Strong correlations of these properties with the dimensionless compressibility are also found, and nearly universal dependences have been numerically identified based on property-specific nondimensionalizations. Generalization of the approach to rigid rods, disks, and variable shaped molecules is possible, including oriented liquid crystalline phases.
AB - An extension of nave ideal mode coupling theory (MCT) and its generalization to treat activated barrier hopping and glassy dynamics in fluids and suspensions composed of nonspherical hard core objects is proposed. An effective center-of-mass description is adopted. It corresponds to a specific type of preaveraging of the dynamical consequences of orientational degrees of freedom. The simplest case of particles composed of symmetry-equivalent interaction sites is considered. The theory is implemented for a homonuclear diatomic shape of variable bond length. The nave MCT glass transition boundary is predicted to be a nonmonotonic function of the length-to-width or aspect ratio and occurs at a nearly unique value of the dimensionless compressibility. The latter quantifies the amplitude of long wavelength thermal density fluctuations, thereby (empirically) suggesting a tight connection between the onset of localization and thermodynamics. Localization lengths and elastic shear moduli for different aspect ratio and volume fraction systems approximately collapse onto master curves based on a reduced volume fraction variable that quantifies the distance from the ideal glass transition. Calculations of the entropic barrier height and hopping time, maximum restoring force, and absolute yield stress and strain as a function of diatomic aspect ratio and volume fraction have been performed. Strong correlations of these properties with the dimensionless compressibility are also found, and nearly universal dependences have been numerically identified based on property-specific nondimensionalizations. Generalization of the approach to rigid rods, disks, and variable shaped molecules is possible, including oriented liquid crystalline phases.
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U2 - 10.1063/1.2405354
DO - 10.1063/1.2405354
M3 - Article
C2 - 17212498
AN - SCOPUS:33846081523
SN - 0021-9606
VL - 126
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 1
M1 - 014505
ER -