Eur. Phys. J. E (2011) 34: 98
https://doi.org/10.1140/epje/i2011-11098-3

Regular Article

Statistical mechanical approach to secondary processes and structural relaxation in glasses and glass formers

A leading model to describe the onset of Johari-Goldstein processes and their relationship with fully cooperative processes

¹ Dipartimento di Fisica, Università “Sapienza”, Piazzale Aldo Moro, 5, 00185, Rome, Italy
² CNR-ISC, Via dei Taurini, 19, 00185, Rome, Italy
³ CNR-IPCF, UOS Roma “Kerberos”, Piazzale Aldo Moro, 5, 00185, Rome, Italy
⁴ Dipartimento di Fisica, Università Roma Tre, Via della Vasca Navale, 84, 00184, Rome, Italy

^* e-mail: luca.leuzzi@cnr.it
^** e-mail: luca.leuzzi@roma1.infn.it

Received: 1 April 2011
Revised: 25 July 2011
Accepted: 26 July 2011
Published online: 23 September 2011

Abstract

The interrelation of dynamic processes active on separated time-scales in glasses and viscous liquids is investigated using a model displaying two time-scale bifurcations both between fast and secondary relaxation and between secondary and structural relaxation. The study of the dynamics allows for predictions on the system relaxation above the temperature of dynamic arrest in the mean-field approximation, that are compared with the outcomes of the equations of motion directly derived within the Mode Coupling Theory (MCT) for under-cooled viscous liquids. By varying the external thermodynamic parameters, a wide range of phenomenology can be represented, from a very clear separation of structural and secondary peak in the susceptibility loss to excess wing structures.