Dielectric relaxation of low-density amorphous ice under pressure.

In situ studies at high pressures show that the dielectric relaxation time tau of low-density amorphous (LDA) ice is more than an order of magnitude longer than that of high density amorphous ice. The increase in tau at the transformation to LDA ice with a simultaneous large density decrease shows that, despite an increase in the average intermolecular distance, the structural change leads to restriction for the orientational diffusion of H2O. The origin is most likely the same as in ice I, i.e., due to the ice rules. This result further stresses the crystallinelike nature of LDA ice.