Unifying the Temperature Dependent Dynamics of Glasses
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arXiv
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| Natura: | Preprint |
| Pubblicazione: |
2024
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| _version_ | 1866911850626547712 |
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| author | Schlenoff, Joseph B. Akkaoui, Khalil |
| author_facet | Schlenoff, Joseph B. Akkaoui, Khalil |
| contents | Strong changes in bulk properties, such as modulus and viscosity, are observed near the glass transition temperature, T_{g}, of amorphous materials. For more than a century, intense efforts have been made to define a microscopic origin for these macroscopic changes in properties. Using transition state theory, we delve into the atomic/molecular level picture of how microscopic localized relaxations, or "cage rattles," translate to macroscopic structural relaxations above T_{g}. Unit motion is broken down into two populations: (1) simultaneous rearrangement occurs among a critical number of units, n_α, which ranges from 1 to 4, allowing a systematic classification of glasses that is compared to fragility; (2) near T_{g}, adjacent units provide additional free volume for rearrangement, not simultaneously, but within the "primitive" lifetime, τ_{1}, of one unit rattling in its cage. Relaxation maps illustrate how Johari-Goldstein \{beta} relaxations stem from the rattle of n_α units. We analyzed a wide variety of glassy materials, and materials with glassy response, using literature data. Our four-parameter equation fits "strong" and "weak" glasses over the entire range of temperatures and also extends to other glassy systems, such as ion-transporting polymers and ferroelectric relaxors. The role of activation entropy in boosting preexponential factors to high "unphysical" apparent frequencies is discussed. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2404_15250 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Unifying the Temperature Dependent Dynamics of Glasses Schlenoff, Joseph B. Akkaoui, Khalil Disordered Systems and Neural Networks Materials Science Soft Condensed Matter Strong changes in bulk properties, such as modulus and viscosity, are observed near the glass transition temperature, T_{g}, of amorphous materials. For more than a century, intense efforts have been made to define a microscopic origin for these macroscopic changes in properties. Using transition state theory, we delve into the atomic/molecular level picture of how microscopic localized relaxations, or "cage rattles," translate to macroscopic structural relaxations above T_{g}. Unit motion is broken down into two populations: (1) simultaneous rearrangement occurs among a critical number of units, n_α, which ranges from 1 to 4, allowing a systematic classification of glasses that is compared to fragility; (2) near T_{g}, adjacent units provide additional free volume for rearrangement, not simultaneously, but within the "primitive" lifetime, τ_{1}, of one unit rattling in its cage. Relaxation maps illustrate how Johari-Goldstein \{beta} relaxations stem from the rattle of n_α units. We analyzed a wide variety of glassy materials, and materials with glassy response, using literature data. Our four-parameter equation fits "strong" and "weak" glasses over the entire range of temperatures and also extends to other glassy systems, such as ion-transporting polymers and ferroelectric relaxors. The role of activation entropy in boosting preexponential factors to high "unphysical" apparent frequencies is discussed. |
| title | Unifying the Temperature Dependent Dynamics of Glasses |
| topic | Disordered Systems and Neural Networks Materials Science Soft Condensed Matter |
| url | https://arxiv.org/abs/2404.15250 |