Fragility from Enthalpy Fluctuations and Fictive-Temperature Dynamics
Abstract
Fragility and fictive temperature are two central measures of glass formation, but their connection is usually expressed indirectly through structural relaxation times or cooling-rate dependence. Here we formulate this connection in terms of configurational enthalpy fluctuations. The time evolution of the fictive temperature during cooling or aging is controlled by the enthalpy--enthalpy correlation function that also determines the frequency-dependent configurational heat capacity. Fragility enters through the strong temperature dependence of the structural relaxation time and therefore controls how rapidly the corresponding enthalpy-relaxation spectrum shifts to long times near the glass transition. This leads to a direct time-domain description of the onset and growth of the fictive-temperature lag, including the Debye limit, and connects calorimetric relaxation, fragility, and nonequilibrium structural arrest within a common framework.
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BibTeX
@misc{bagchi2026fragility,
title = {{Fragility from Enthalpy Fluctuations and Fictive-Temperature Dynamics}},
author = {Biman Bagchi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.07396},
eprint = {2609.07396},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.07396},
}
RIS
TY - UNPB
TI - Fragility from Enthalpy Fluctuations and Fictive-Temperature Dynamics
AU - Biman Bagchi
PY - 2026
DA - 2026/09/07
PB - arXiv
DO - 10.48550/arxiv.2609.07396
UR - https://arxiv.org/abs/2609.07396
AB - Fragility and fictive temperature are two central measures of glass formation, but their connection is usually expressed indirectly through structural relaxation times or cooling-rate dependence. Here we formulate this connection in terms of configurational enthalpy fluctuations. The time evolution of the fictive temperature during cooling or aging is controlled by the enthalpy--enthalpy correlation function that also determines the frequency-dependent configurational heat capacity. Fragility enters through the strong temperature dependence of the structural relaxation time and therefore controls how rapidly the corresponding enthalpy-relaxation spectrum shifts to long times near the glass transition. This leads to a direct time-domain description of the onset and growth of the fictive-temperature lag, including the Debye limit, and connects calorimetric relaxation, fragility, and nonequilibrium structural arrest within a common framework.
ER -