Semischematic model for the center-of-mass dynamics in supercooled molecular liquids

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics

Volumn 57, Issue 2, 1998, Pages 1485-1488

  Fabbian, Linda ^a   Sciortino, Francesco ^a   Thiery, Filippo ^a   Tartaglia, Piero ^a  

^a UNIVERSITÀ DI ROMA LA SAPIENZA   (Italy)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000667808     PISSN: 1063651X     EISSN: None     Source Type: Journal    
DOI: 10.1103/PhysRevE.57.1485     Document Type: Article

References (39)

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14. Extension of the ideal MCT to the case where current density fluctuations are included among the slow modes generates the so-called extended MCT, in which phonon assisted hopping processes are also considered as candidate for structural relaxation processes. These processes smear out the ideal liquid-glass transition. See, for example, W. Götze and A. Sjögren, Transp. Theory Stat. Phys. 24, 801 (1995).
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28. The ideal MCT equations reduce to the schematic model with memory function m(t)∝φ02(t) if the q dependence of the correlators is condensed in a single representative q0 vector, i.e., if the structure factor is Sq∝δ(q-q0) [see E. Leutheusser Phys. Rev. A 29, 2765 (1984)]. We call our model semischematic because we retain all the q dependence of the translational correlators but we model the coupling with the angular correlation functions with a single q-independent value χR
29. The time evolution of all correlators in the supercooled regime follows a two-step decay. After the short time microscopic dynamics, the correlators approach a plateau value fq. The decay after the plateau value is commonly referred to as α relaxation.
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33. In principle one could decide not to enforce the condition TcMCT=TcMD and to fix TcMCT independently. This introduces a new external parameter (i.e., the value of TcMCT) and makes the comparison between theory and simulation more subtle.
34. We recall that the MD nonergodicity parameter and the critical amplitudes are obtained fitting the calculated time evolution of the density correlator in the early α region using the von Schweidler’s law (4). (See Ref. 14).
35. Due to the scale invariance of the MCT equations for the dynamics in the α-relaxation region [Eq. (1)], the values for the relaxation times τq are defined up to a q-independent multiplicative number. This time scale depends on a microscopic characteristic time, which cannot be calculated within the mode-coupling approximations. Therefore we arbitrarily choose the time scale in the comparison between theory and simulations for hq(1), hq(2), and τqK.
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