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Phonon-assisted proton tunneling in the hydrogen-bonded dimeric selenates of Cs3H(SeO4)2

Authors :
Takahiko Sasaki
Yuka Ikemoto
Hiroshi Matsui
Kazuki Shimatani
Yasumitsu Matsuo
Source :
The Journal of Chemical Physics. 152:154502
Publication Year :
2020
Publisher :
AIP Publishing, 2020.

Abstract

In phases III and IV of Cs3H(SeO4)2, the vibrational state and intrabond transfer of the proton in the dimeric selenates are systematically studied with a wide range of absorbance spectra, a spin–lattice relaxation rate of 1H-NMR (T1−1), and DFT calculations. The OH stretching vibrations have extremely broad absorption at around 2350 (B band) and 3050 cm−1 (A band), which originate from the 0–1 and 0–2 transitions in the asymmetric double minimum potential, respectively. The anharmonic-coupling calculation makes clear that the A band couples not only to the libration but also to the OH bending band. The vibrational state (nano-second order) is observed as the response of the proton basically localized in either of the two equivalent sites. The intrabond transfer between those sites (pico-second order) yields the protonic fluctuation reflected in T1−1. Together with the anomalous absorption [νp2 phonon, libration, tetrahedral deformation (δ440), and 610-cm−1 band], we have demonstrated that the intrabond transfer above 70 K is dominated by the thermal hopping that is collectively excited at 610 cm−1 and the phonon-assisted proton tunneling (PAPT) relevant to the tetrahedral deformation [PAPT(def)]. Below 70 K, T1−1 is largely enhanced toward the antiferroelectric ordering and the distinct splitting emerges in the libration, which dynamically modulates the O(2)–O′(2) distance of the dimer. The PAPT(lib) associated with the libration is confirmed to be a driving force of the AF ordering.

Details

ISSN :
10897690 and 00219606
Volume :
152
Database :
OpenAIRE
Journal :
The Journal of Chemical Physics
Accession number :
edsair.doi.dedup.....af54dfba28025d932396048afd741540
Full Text :
https://doi.org/10.1063/1.5145108