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Temperature-Dependent Hydrophobic Crossover Length Scale and Water Tetrahedral Order

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journal contribution
posted on 08.02.2018, 00:00 by Xiangen Wu, Wanjun Lu, Louis M. Streacker, Henry S. Ashbaugh, Dor Ben-Amotz
Experimental Raman multivariate curve resolution and molecular dynamics simulations are performed to demonstrate that the vibrational frequency and tetrahedrality of water molecules in the hydration-shells of short-chain alcohols differ from those of pure water and undergo a crossover above 100 °C (at 30 MPa) to a structure that is less tetrahedral than pure water. Our results demonstrate that the associated crossover length scale decreases with increasing temperature, suggesting that there is a fundamental connection between the spectroscopically observed crossover and that predicted to take place around idealized purely repulsive solutes dissolved in water, although the water structure changes in the hydration-shells of alcohols are far smaller than those associated with an idealized “dewetting” transition.