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Supercooled confined water and the mode coupling crossover temperature
1Dipartimento di Fisica "E. Amaldi," Universita "Roma Tre," and Istituto Nazionale per la Fisica della Materia, Unita di Ricerca Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy.
Physical Review Letters
|November 4, 2000
Summary
Supercooled water in silica pores exhibits distinct molecular dynamics. Near the pore walls, water is always below the mode coupling crossover temperature, while central water approaches it upon cooling.
Area of Science:
- Physical Chemistry
- Materials Science
- Computational Physics
Background:
- Supercooled water dynamics are complex and not fully understood.
- Confinement effects significantly alter water's properties.
- Mode coupling theory provides a framework for understanding liquid dynamics near a glass transition.
Purpose of the Study:
- To investigate the single-particle dynamics of supercooled water confined in a silica pore.
- To identify different dynamical regimes within the confined water.
- To compare experimental observations with predictions from mode coupling theories.
Main Methods:
- Molecular dynamics simulations were employed.
- The study focused on supercooled water confined within a hydrophilic silica pore.
- Analysis involved examining diffusion coefficients and relaxation times.
Main Results:
- Two distinct dynamical regimes were observed in the confined water.
- Water near the hydrophilic substrate remained below the mode coupling crossover temperature (T(C)) even at ambient temperatures.
- Water in the center of the pore (free water) approached T(C) upon supercooling, consistent with theoretical predictions.
Conclusions:
- Confinement in silica pores leads to heterogeneous dynamics in supercooled water.
- The findings support mode coupling theory predictions for the dynamics of bulk-like water under confinement.
- Key parameters like crossover temperature and exponent were extracted for the free water regime.