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

P8.46Thu 811:10-14:00Presence and absence of crystallization nuclei inhigh-density amorphous iceMarkus Seidl, 1 Katrin Winkel, 1 Philip H. Handle, 1 Gerhard Zifferer, 2 Erwin Mayer, 3and Thomas Loerting 11 Institute of Physical Chemistry, University of Innsbruck, Innrain 52a, 6020, Innsbruck,Austria2 Department of Physical Chemistry, University of Vienna, Wien, Austria3 Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck,Innsbruck, AustriaThere is still much debate on the nature of amorphous ices, in particular, whether amorphous icesare glasses or rather consist of nanocrystallites [1]. For example, high-density amorphous ice(HDA) has been characterized as heterogeneous material, supporting the ”contra-glass” view ofHDA (e. g. , in [2]). Here we investigate the crystallization behavior of HDA at different pressuresbetween 0.1 and 0.3 GPa while isobaric heating, both for samples prepared by pressure-inducedamorphization of hexagonal ice (Ih) [3] and samples prepared by isothermal decompression ofvery high-density amorphous ice (VHDA) [4]. We show that the crystallization behavior impliesheterogeneous nature of the former, but homogeneous nature of the latter form of HDA, eventhough the radial distribution functions are very similar [5]. It is, therefore, highly important todifferentiate between both forms of HDA and to consider them as different materials. We interpretthe differences in terms of presence and absence of specific crystallization nuclei in HDA directlymade from ice Ih and HDA made from VHDA, respectively. Furthermore, we suggest that at0.3 GPa the crystallization nuclei present in the former material transform into high-pressure icenuclei, i. e. , a phase transition of crystallization seeds on the nm-length scale takes place.[1] T. Loerting et al. , Adv. Chem. Phys. 143 (2009) 29.[2] G. P. Johari, Phys. Chem. Chem. Phys. 2 (2000) 1567.[3] O. Mishima et al. , Nature 310 (1984) 393.[4] K. Winkel et al. , J. Chem. Phys. 128 (2008) 044510.[5] T. Loerting et al. , Phys. Chem. Chem. Phys. , DOI: 10. 1039/c0cp02600j.46