TY - JOUR
T1 - On the role of intermolecular vibrational motions for ice polymorphs. II. Atomic vibrational amplitudes and localization of phonons in ordered and disordered ices
AU - Tanaka, Hideki
AU - Yagasaki, Takuma
AU - Matsumoto, Masakazu
N1 - Funding Information:
The authors are grateful to Professors H. Adachi and H. Goto for helpful discussion. The present work was supported by JSPS KAKENHI (Grant No. 17K19106), and MEXT as “Priority Issue on Post-Kcomputer” (Development of new fundamental technologies for high-efficiency energy creation, conversion/storage, and use), and Research Center for Computational Science in providing computational resource.
Publisher Copyright:
© 2020 Author(s).
PY - 2020/2/21
Y1 - 2020/2/21
N2 - We investigate the vibrational amplitudes and the degree of the phonon localization in 19 ice forms, both crystalline and amorphous, by a quasi-harmonic approximation with a reliable classical intermolecular interaction model for water. The amplitude in the low pressure ices increases with compression, while the opposite trend is observed in the medium and high pressure ices. The amplitude of the oxygen atom does not differ from that of hydrogen in low pressure ices apart from the contribution from the zero-point vibrations. This is accounted for by the coherent but opposite phase motions in the mixed translational and rotational vibrations. A decoupling of translation-dominant and rotation-dominant motions significantly reduces the vibrational amplitudes in any ice form. The amplitudes in ice III are found to be much larger than any other crystalline ice form. In order to investigate the vibrational mode characteristics, the moment ratio of the atomic displacements for individual phonon modes, called the inverse participation ratio, is calculated and the degree of the phonon localization in crystalline and amorphous ices is discussed. It is found that the phonon modes in the hydrogen-ordered ice forms are remarkably spread over the entire crystal having propagative or diffusive characteristic, while many localized modes appear at the edges of the vibrational bands, called dissipative modes, in the hydrogen-disordered counterparts. The degree of localization is little pronounced in low density amorphous and high density amorphous due to disordering of oxygen atoms.
AB - We investigate the vibrational amplitudes and the degree of the phonon localization in 19 ice forms, both crystalline and amorphous, by a quasi-harmonic approximation with a reliable classical intermolecular interaction model for water. The amplitude in the low pressure ices increases with compression, while the opposite trend is observed in the medium and high pressure ices. The amplitude of the oxygen atom does not differ from that of hydrogen in low pressure ices apart from the contribution from the zero-point vibrations. This is accounted for by the coherent but opposite phase motions in the mixed translational and rotational vibrations. A decoupling of translation-dominant and rotation-dominant motions significantly reduces the vibrational amplitudes in any ice form. The amplitudes in ice III are found to be much larger than any other crystalline ice form. In order to investigate the vibrational mode characteristics, the moment ratio of the atomic displacements for individual phonon modes, called the inverse participation ratio, is calculated and the degree of the phonon localization in crystalline and amorphous ices is discussed. It is found that the phonon modes in the hydrogen-ordered ice forms are remarkably spread over the entire crystal having propagative or diffusive characteristic, while many localized modes appear at the edges of the vibrational bands, called dissipative modes, in the hydrogen-disordered counterparts. The degree of localization is little pronounced in low density amorphous and high density amorphous due to disordering of oxygen atoms.
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U2 - 10.1063/1.5139697
DO - 10.1063/1.5139697
M3 - Article
C2 - 32087662
AN - SCOPUS:85079805334
SN - 0021-9606
VL - 152
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 7
M1 - 074501
ER -