| Autor: |
Rescigno M; Dipartimento di Fisica, Università di Roma La Sapienza, 00185 Roma, RM, Italy., Lucioli M; Dipartimento di Fisica, Università di Roma La Sapienza, 00185 Roma, RM, Italy., Alabarse FG; Elettra Sincrotrone Trieste, 34149 Basovizza, Trieste, Italy., Ranieri U; Dipartimento di Fisica, Università di Roma La Sapienza, 00185 Roma, RM, Italy., Frick B; Institut Laue-Langevin, 38042 Grenoble Cedex 9, France., Coasne B; Université Grenoble Alpes, CNRS, LIPhy, 38000 Grenoble, France., Bove LE; Dipartimento di Fisica, Università di Roma La Sapienza, 00185 Roma, RM, Italy.; Sorbonne Université, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), 75252 Paris, France.; Laboratory of Quantum Magnetism, Institute of Physics, École Polytechnique Fedeerale de Lausanne, Lausanne CH-1015, Switzerland. |
| Abstrakt: |
The dynamical properties of water molecules confined in the unidirectional hydrophilic nanopores of AlPO 4 -54 are investigated with quasi-elastic neutron scattering as a function of temperature down to 118 K. AlPO 4 -54 has among the largest pores known for aluminophosphates and zeolites (about 1.3 nm), though they are small enough to prevent water crystallization due to the high degree of confinement. Water molecular diffusion into the pore is here measured down to 258 K. Diffusion is slower than in bulk water and has an activation energy of E a = (20.8 ± 2.8) kJ/mol, in agreement with previous studies on similar confining media. Surprisingly, local hydrogen dynamics associated with water reorientation is measured down to temperatures (118 K), i.e., well below the expected glass transition temperature of bulk water. The reorientational time scale shows the well-known non-Arrhenius behavior down to the freezing of water mass diffusion, while it shows a feeble temperature dependence below. This fast local dynamics, of the order of fractions of nanoseconds, is believed to take place in the dense, highly disordered amorphous water occupying the pore center, indicating its possible plastic nature. |
