Dynamics enhanced by HCl doping triggers 60% Pauling entropy release at the ice XII–XIV transition

Abstract

The pressure–temperature phase diagram of ice displays a perplexing variety of structurally distinct phases. In the century-long history of scientific research on ice, the proton-ordered ice phases numbered XIII through XV were discovered only recently. Despite considerable effort, none of the transitions leading from the low-temperature ordered ices VIII, IX, XI, XIII, XIV and XV to their high-temperature disordered counterparts were experimentally found to display the full Pauling entropy. Here we report calorimetric measurements on suitably high-pressure-treated, hydrogen chloride-doped ice XIV that demonstrate just this at the transition to ice XII. Dielectric spectroscopy on undoped and on variously doped ice XII crystals reveals that addition of hydrogen chloride, the agent triggering complete proton order in ice XIV, enhances the precursor dynamics strongest. These discoveries provide new insights into the puzzling observation that different dopants trigger the formation of different proton-ordered ice phases.

Doping-enhanced dipolar dynamics in ice V as a precursor of hydrogen ordering in ice XIII

“…Conversely, with a focus on exploring dynamical aspects leading to the ice V → ice XIII phase transition, here we report on the ambient-pressure dipolar response not only of undoped ice V but also of KOH and HCl doped crystals. This paper complements a recent experimental study of pure and doped ice XII [53]. For this high-pressure generated ice, HCl doping leads to the formation of ice XIV, a hydrogen ordered phase [5].…”

“…[25] and ice XII(HCl) Ref. [53], which were found to eventually lead to the ordered phases ice XI and ice XIV, respectively. Hence, monitoring the dielectric response of ice V(HCl) down to lower temperatures allowed us to study the ordering transition in this ice phase, as will be demonstrated in the following.…”

“…The notation of a protonated or deuterated dopant is meant to imply the protonation or deuteration of the ice or hydrate lattice as well. This figure contains data on KOH-doped ice I h /XI [64,65], KOD-doped ice I h /XI [16], RbOH-doped ice I h /XI [14], HCl-doped ice V/XIII from this paper, and HCl-doped ice XII/XIV [53]. The data on the potassium hydroxide doped clathrate hydrates refer to the guest molecules THF (tetrahydrofuran, doped with KOH [18,70] or KOD [20]), ACE (acetone, with KOH) [21], or TMO (trimethylene oxide, with KOH) [21].…”

Deeply supercooled aqueous LiCl solution studied by frequency-resolved shear rheology

“…The dashed lines refer to power laws ε ′′ ∝ ν -α as indicated. For comparison, frame (b) shows dielectric loss spectra for the crystalline ices IV, V, 51 VI, and XII 50 as well as for CO 2 -filled clathrate hydrate. Note that a peak maximum cannot be identified clearly for the data of ice VI and of the CO 2 -filled clathrate hydrate.…”

“…In the astrophysical literature (e.g., Ref. 33), such high-surface-area samples are often called porous ASW (p-ASW) and they are prone to an uncontrolled uptake of background gas 51 VI, and XII 50 are represented as symbols, those of LDA and HDA as dashed lines. The half-filled points for the CO 2 -filled clathrate hydrate and for ice VI were obtained by matching the high-frequency flank of their main process to that of the HGW sample.…”