Enthalpy Change from Pure Cubic Ice Ic to Hexagonal Ice Ih

Christina M Tonauer; Keishiro Yamashita; Leonardo Del Rosso; Milva Celli; Thomas Loerting

doi:10.1021/acs.jpclett.3c00408

Enthalpy Change from Pure Cubic Ice I_c to Hexagonal Ice I_h

J Phys Chem Lett. 2023 Jun 1;14(21):5055-5060. doi: 10.1021/acs.jpclett.3c00408. Epub 2023 May 25.

Authors

Christina M Tonauer¹, Keishiro Yamashita¹, Leonardo Del Rosso², Milva Celli², Thomas Loerting¹

Affiliations

¹ Institute of Physical Chemistry, University of Innsbruck, Innrain 52c, A-6020 Innsbruck, Austria.
² Consiglio Nazionale delle Ricerche, Istituto di Fisica Applicata 'Nello Carrara', via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy.

Abstract

The preparation of pure cubic ice without hexagonal stacking faults has been realized only recently by del Rosso et al. ( Nat. Mater. 2020, 19, 663-668) and Komatsu et al. ( Nat. Commun. 2020, 11, 464). With our present calorimetric study on the transition from pure cubic ice to hexagonal ice we are able to clarify the value of the enthalpy change ΔH_c→h to be -37.7 ± 2.3 J mol^-1. The transition temperature is identified as 226 K, much higher than in previous work on ice I_sd. This is due to a catalytic effect of hexagonal faults on the transition, but even more importantly due to a relaxation exotherm that was not properly identified in the past.