Crucial role of fragmented and isolated defects in persistent relaxation of deeply supercooled water
| Autor: | Iwao Ohmine, Shinji Saito, Biman Bagchi |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Materials science
Properties of water 010304 chemical physics Melting temperature General Physics and Astronomy FOS: Physical sciences Condensed Matter - Soft Condensed Matter 010402 general chemistry Breakup 01 natural sciences 0104 chemical sciences Molecular dynamics chemistry.chemical_compound chemistry Fragmentation (mass spectrometry) Chemical physics 0103 physical sciences Molecule Soft Condensed Matter (cond-mat.soft) Physical and Theoretical Chemistry Glass transition Supercooling |
| Popis: | Properties of water have been well elucidated for temperatures above $\sim$230 K and yet mysteries remain in the deeply supercooled region. By performing extensive molecular dynamics simulations on this supercooled region, we find that structural and dynamical instabilities are hidden in the experimentally inaccessible region between 235 K and 150 K. We find a hitherto undiscovered fragmentation from 220 K to 190 K, which is the break-up of large clusters consisting of molecules with locally distorted tetrahedral structure into small pieces with one or two isolated defects. The fragmentation leads to considerable changes in the relaxation dynamics of water. We reveal a crucial role of specific three-coordinated defects in slow but persistent structural relaxation. The presence of relaxation due to these specific defects makes water glass transition temperature $T_{\rm g}$ (= 136 K) extremely low and explains why the $T_{\rm g}$ of water is $\sim$ 1/2 of the melting temperature Tm, much lower than the commonly obeyed 2/3 rule of $T_{\rm g}/T_{\rm m}$. 24 pages, 5 figures, and 15 pages and 6 figures in supplementary material |
| Databáze: | OpenAIRE |
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