title: Experimental evidence for a crossover between two distinct mechanisms of amorphization in ice Ih under pressure.
abstract: We report neutron scattering data which reveal the central role of phonon softening leading to a negative melting line, solid-state amorphization, and negative thermal expansion of ice. We find that pressure-induced amorphization is due to mechanical melting at low temperatures, while at higher temperatures amorphization is governed by thermal melting (violations of Born's and Lindemann's criteria, respectively). This confirms earlier conjectures of a crossover between two distinct amorphization mechanisms and provides a natural explanation for the strong annealing observed in high-density amorphous ice.
authors.affiliation: Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: Thierry
authors.initials: T
authors.lastname: Strässle
authors.forename: Stefan
authors.initials: S
authors.lastname: Klotz
authors.forename: Gérard
authors.initials: G
authors.lastname: Hamel
authors.forename: Michael M
authors.initials: MM
authors.lastname: Koza
authors.forename: Helmut
authors.initials: H
authors.lastname: Schober