The dynamic susceptibility in glass forming molecular liquids:: The search for universal relaxation patterns II

被引:64
作者
Blochowicz, T [1 ]
Gainaru, C
Medick, P
Tschirwitz, C
Rössler, EA
机构
[1] Tech Univ Darmstadt, D-64289 Darmstadt, Germany
[2] Univ Bayreuth, D-95440 Bayreuth, Germany
关键词
D O I
10.1063/1.2178316
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The susceptibility spectra of ten molecular glass formers are completely interpolated by an extension of the generalized gamma distribution of correlation times. The data cover at least 15 decades in frequency and the interpolation includes both alpha peak and excess wing. It is shown that the line shape parameters and the time constant of the alpha relaxation are related to each other. Master curves are identified by a scaling procedure that involves only three parameters, namely, the glass transition temperature T-g, the fragility m, and the excess wing exponent at T-g. This holds independent of whether a further secondary relaxation peak is present or not. Above a crossover temperature T-x this unique evolution of the line shape parameters breaks down, and a crossover to a simple peak susceptibility without excess wing is observed. Here, the frequency-temperature superposition principle holds in good approximation up to temperatures well above the melting point. It turns out that the crossover coincides with the temperature at which the low-temperature Vogel-Fulcher law starts to fail upon heating. Thus, the so-called Stickel temperature gets a more physical meaning as it marks a qualitative change in the evolution of the susceptibility spectra of glass formers. Moreover, the interrelation of the line shape parameters can explain why the "Nagel scaling" works in some approximation. Our study demonstrates that the excess wing in molecular glass formers is a secondary relaxation, which is linked to the alpha process in a unique way. (c) 2006 American Institute of Physics.
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页数:11
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共 41 条
[1]   Reexamination of the evolution of the dynamic susceptibility of the glass former glycerol -: art. no. 011504 [J].
Adichtchev, S ;
Blochowicz, T ;
Tschirwitz, C ;
Novikov, VN ;
Rössler, EA .
PHYSICAL REVIEW E, 2003, 68 (01) :10-115041
[2]   Evolution of the dynamic susceptibility of simple glass formers in the strongly supercooled regime [J].
Adichtchev, S ;
Blochowicz, T ;
Gainaru, C ;
Novikov, VN ;
Rössler, EA ;
Tschirwitz, C .
JOURNAL OF PHYSICS-CONDENSED MATTER, 2003, 15 (11) :S835-S847
[3]   Anomaly of the nonergodicity parameter and crossover to white noise in the fast relaxation spectrum of a simple glass former -: art. no. 055703 [J].
Adichtchev, SV ;
Benkhof, S ;
Blochowicz, T ;
Novikov, VN ;
Rössler, E ;
Tschirwitz, C ;
Wiedersich, J .
PHYSICAL REVIEW LETTERS, 2002, 88 (05) :4
[4]   Nonresonant dielectric hole burning in neat and binary organic glass formers -: art. no. 224511 [J].
Blochowicz, T ;
Rössler, EA .
JOURNAL OF CHEMICAL PHYSICS, 2005, 122 (22)
[5]   The spectral density in simple organic glass formers:: Comparison of dielectric and spin-lattice relaxation [J].
Blochowicz, T ;
Kudlik, A ;
Benkhof, S ;
Senker, J ;
Rössler, E ;
Hinze, G .
JOURNAL OF CHEMICAL PHYSICS, 1999, 110 (24) :12011-12022
[6]   Beta relaxation versus high frequency wing in the dielectric spectra of a binary molecular glass former -: art. no. 225701 [J].
Blochowicz, T ;
Rössler, EA .
PHYSICAL REVIEW LETTERS, 2004, 92 (22) :225701-1
[7]   Susceptibility functions for slow relaxation processes in supercooled liquids and the search for universal relaxation patterns [J].
Blochowicz, T ;
Tschirwitz, C ;
Benkhof, S ;
Rössler, EA .
JOURNAL OF CHEMICAL PHYSICS, 2003, 118 (16) :7544-7555
[8]  
Blochowicz T., 2003, THESIS U BAYREUTH
[9]   Depolarized light scattering study of glycerol [J].
Brodin, A ;
Rössler, EA .
EUROPEAN PHYSICAL JOURNAL B, 2005, 44 (01) :3-14
[10]  
Brodin A, 2002, PHYS REV E, V65, DOI 10.1103/PhysRevE.65.051503