Understanding the difference in the stretched structural relaxations probed by dielectric and enthalpic studies of glass forming substances
| Autor: | Xu-Dong Li, Xiao Jin, Zijing Li, Yingdan Liu, Shidong Feng, Li-Min Wang |
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| Rok vydání: | 2022 |
| Předmět: | |
| Zdroj: | The Journal of Chemical Physics. 157:184501 |
| ISSN: | 1089-7690 0021-9606 |
| DOI: | 10.1063/5.0122186 |
| Popis: | We investigated the stretched dynamics of the structural relaxation in molecular glass formers by using dielectric and thermal (or enthalpic) relaxations. The dielectric stretching exponents β die are determined by the Havriliak–Negami function, while the enthalpic β TNMH is quantified by using the Tool–Narayanaswamy–Moynihan–Hodge formalism. We found β TNMH is anticorrelated with the degree of freedom, a molecule addressed by the concept of beads. Referring to the reported relation of β die to the dipole moment μ, we proposed a combined parameter of μ2* beads, which can rationalize the difference in stretching exponents obtained by dielectric and enthalpic relaxations. For the majority of glass-forming molecules, the difference is trivial, but for those molecules with both unusually high dipole moments and flexibility, a large difference is obvious. The interplay of the degree of freedom and dielectric dipole–dipole interaction in molecular dynamics is addressed. |
| Databáze: | OpenAIRE |
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