Water as a Levy rotor
| Autor: | Faux, David A., Rahaman, Arifah A., McDonald, Peter J. |
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| Rok vydání: | 2021 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevLett.127.256001 |
| Popis: | A probability density function describing the angular evolution of a fixed-length atom-atom vector as a L\'{e}vy rotor is derived containing just two dynamical parameters: the L\'{e}vy parameter $\alpha$ and a rotational time constant $\tau$. A L\'{e}vy parameter $\alpha\!<\!2$ signals anomalous (non-Brownian) motion. A molecular dynamics simulation of water at 298\,K validates the probability density function for the intra-molecular $^1$H--$^1$H dynamics of water. The rotational dynamics of water is found to be approximately Brownian at sub-picosecond time intervals but becomes increasingly anomalous at longer times due to hydrogen-bond breaking and reforming. The rotational time constant lies in the range $8 \! < \! \tau \! < \! 11$\,ps. The L\'{e}vy rotor model is used to estimate the intra-molecular contribution to the longitudinal nuclear-magnetic-resonance relaxation rate $R_{1,{\rm intra}}$ due to dipolar $^1$H--$^1$H interactions. It is found that $R_{1,{\rm intra}}$ contributes $65\,\pm 7$\% to the overall relaxation rate of water at room temperature. Comment: 4 pages, 3 figures, for the main paper. Supplementary material included and in the right place |
| Databáze: | arXiv |
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