Hydrogen-bond memory and water-skin supersolidity resolving Mpemba Paradox
Chang Q Sun, NTU/Singapore, Ecqsun@ntu.edu.sg
We show that hydrogen bond (O:H-O) possesses memory (Panel a, H-bond linear velocity derived from measurements) to emit energy at a rate depending on its initial storage and that water skin exhibits supersolidity (b, Raman confirmation) to grade thermal conductivity with heat flowing outwardly. These identities resolve intrinsically the Mpemba paradox – (c) hotter water freezes faster than colder water does with (d) skin being warmer than the bulk. Heating stores energy into water by stretching the O:H nonbond and shortening the H-O bond via Coulomb coupling; cooling does oppositely, like releasing a highly deformed bungee, to emit heat at a rate of history dependence. Skin molecular undercoordination grades the local mass density, specific heat, and thermal conductivity, favoring heat outward flowing. Convection alone creates no Mpemba effect. Being sensitive to the source volume and the drain temperature, Mpemba effect proceeds only in the strictly non-adiabatic source-drain interface with a relaxation time that drops exponentially with the rise of the initial temperature of the source. Reproduction of the Mpemba effect (c, d) verified the validity and consistency of our recent findings on the structure order, O:H-O bond potentials, and physical anomalies of water ice [1-6].
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2.Y. Huang, X. Zhang, Z. Ma, Y. Zhou, G. Zhou, and C.Q. Sun, Hydrogen-bond asymmetric local potentials in compressed ice. J. Phys. Chem. B, 2013. 117(43): 13639-13645.
3.C.Q. Sun, X. Zhang, J. Zhou, Y. Huang, Y. Zhou, and W. Zheng, Density, Elasticity, and Stability Anomalies of Water Molecules with Fewer than Four Neighbors. J Phys. Chem. Lett. 2013. 4: 2565-2570.
4.C.Q. Sun, X. Zhang, X. Fu, W. Zheng, J.-l. Kuo, Y. Zhou, Z. Shen, and J. Zhou, Density and phonon-stiffness anomalies of water and ice in the full temperature range. J. Phys. Chem. Lett. 2013. 4: 3238-3244.
5.C.Q. Sun, X. Zhang, and W.T. Zheng, Hidden force opposing ice compression. Chem Sci. 2012. 3: 1455-1460.
6.C.Q. Sun, Relaxation of the Chemical Bond. Springer Series in Chem Phys. Vol. 108. 807 pp., 2014 Heidelberg.