8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Thu 811:10-14:00P8.17Structural relaxation times in high-density amorphousice (HDA)Philip H. Handle, 1 Markus Seidl, 1 Erwin Mayer, 2 and Thomas Loerting 11 University of Innsbruck, Institute of Physical Chemistry, Innrain 52a, 6020, Innsbruck,Austria2 University of Innsbruck, Institute of General, Inorganic and Theoretical Chemistry,Innsbruck, AustriaSolid water (H 2 O) exists in a variety of different forms. Besides common hexagonal ice (Ih)today 15 different crystalline and three different amorphous forms are known. It is underdiscussion whether the amorphous forms are glassy (related to liquid water [1]) or nano-crystalline(related to ice). In case of high-density amorphous ice (HDA), this question has been addressedin some studies [2-5], yet remains controversial. In our work we determine the structuralrelaxation times of HDA at elevated pressures (0.1 and 0.2 GPa) and different temperatures(125-135 K) on the basis of differential scanning calorimetry (DSC) at 1 bar. We show thatthe HDA→LDA transition temperature depends strongly on the thermal history and so it isused as basis for the determination of the structural relaxation time. Our data suggest thatat 135 K the structural relaxation time is only slightly higher than 100 s, i.e. HDA is on theborderline to the glass-to-liquid transition. Furthermore those relaxation times allow us to estimatethe glass-to-liquid transition temperature of HDA at 0. 1 and 0. 2 GPa by extrapolation of our data.[1] P. H. Poole, et al. , Nature 360, 324-328 (1992)[2] J. S. Tse, et al. ; Nature 400, 647-649 (1999)[3] O. Mishima, J. Chem. Phys. 115, 4199-4202 (2001)[4] O. Andersson, Phys. Rev. Lett. 95, 205503-205507 (2005)[5] M. Seidl, et al. , Phys. Rev. B 83, 100201-1-100201-4 (2011)17