Unusual Molecular Dynamics in H2O Ice - Seminário FMT
2ª feira, 10/02, 14h. IFUSP - Ed. Alessandro Volta / Bloco C - Sala de Seminários José Roberto Leite
John J. Neumeier, Physics Department, Montana State University
The low-pressure form of solid H2O may be man’s most well-known solid, but it is highly complex, and in many ways poorly understood. In 2011 we realized that ice’s thermal expansion had never been measured very well. Our experiments have determined the linear thermal expansion of ice along its principal crystallographic directions with a relative resolution of 1 part per billion. This resolution is about 8,000 times better than previous measurements. Along with other previously-unknown features, the data reveal an unusual phase transition at 100 K. In D2O ice the transition moves to 125 K. This is one of the largest-known isotope effects in nature. Measurements of the dielectric properties reveal that the transition is associated with thermally-stimulated rotations of the H2O molecules that begin at 100 K and persist till melting. These excitations are well-described as solitary waves, or solitons, which reveals a new perspective on the dynamics of H2O molecules in ice.
This research was realized with support from NSF Grant DMR-1204146 and the efforts of David T.W. Buckingham, Sueli H. Masunaga, and Yi-Kuo Yu.