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Theoretical studies of water clusters containing OH{e}HO structure and electron-hydrogen bond
https://ir.soken.ac.jp/records/205
https://ir.soken.ac.jp/records/2058b53355b-8803-49c3-aad8-2cef1665460d
| 名前 / ファイル | ライセンス | アクション |
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要旨・審査要旨 / Abstract, Screening Result (369.2 kB)
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本文 (6.0 MB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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| 公開日 | 2010-02-22 | |||||
| タイトル | ||||||
| タイトル | Theoretical studies of water clusters containing OH{e}HO structure and electron-hydrogen bond | |||||
| タイトル | ||||||
| タイトル | Theoretical studies of water clusters containing OH{e}HO structure and electron-hydrogen bond | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
| 資源タイプ | thesis | |||||
| 著者名 |
鶴澤, 武士
× 鶴澤, 武士 |
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| フリガナ |
ツルサワ, タケシ
× ツルサワ, タケシ |
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| 著者 |
TSURUSAWA, Takeshi
× TSURUSAWA, Takeshi |
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| 学位授与機関 | ||||||
| 学位授与機関名 | 総合研究大学院大学 | |||||
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| 学位名 | 博士（理学） | |||||
| 学位記番号 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 総研大乙第74号 | |||||
| 研究科 | ||||||
| 値 | 数物科学研究科 | |||||
| 専攻 | ||||||
| 値 | 07 構造分子科学専攻 | |||||
| 学位授与年月日 | ||||||
| 学位授与年月日 | 2000-03-24 | |||||
| 学位授与年度 | ||||||
| 値 | 1999 | |||||
| 要旨 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | Water cluster anions (H2O)n- are the model systems for the hydrated electron. Experimentally, small cluster anions with n = 2, 3, ..., have been found in the mass spectra and these photoelectron spectra have been observed. Recently, the infrared spectra for n = 5, 6, ... , have also been reported. He has studied small water cluster anions (H2O)n- for n = 2, 3, 4 and 6 with ab initio MO methods. It has been believed that for small cluster anions, the excess electron is bound by the dipole moment of the neutral cluster and is distributed outside of the cluster. This type of cluster anions are the dipole bound electron type anions. On the other hand, for larger clusters with n > 32 or so it has been shown that by the quantum simulation calculations that the excess electron is trapped inside the cluster. This type of cluster anions are the internally trapped electron type anions. In the (H2O)n-, especially for the dipole bound electron type anions, the excess electron has a diffuse nature, and therefore he uses diffuse function sets to describe the excess electron in the calculations. Because the optimized geometries of the (H20)n- are sensitive to the electron correlation, it is necessary to include the electron correlation at least MP2 level in the geometry optimization process. He found that there exist the internally trapped electron type isomers for small cluster anions as well as the dipole bound electron type isomers. For the dipole bound electron type isomers, the singly occupied molecular orbital (SOMO) is very diffuse and the effect of the excess electron on the structure of the core cluster is small. Consequently, the optimized structures for the dipole bound electron type isomers are close to those of the neutral clusters. For the internally trapped electron type isomers, the electron plays an important role to hold the stable structure. In the internally trapped electron anions he obtained for dimer, trimer, tetramer and one of hexamer anions, there is no hydrogen bond between the fragments surrounding the electron. For the internally trapped electron type anions, he calls the structure of the electron and the surrounding OH bonds OH{e}HO structure. For (H2O)n-, he found that the SUMO extent measure (SEM), which is the volume of the sphere containing a half of the SUMO electron and a measure of the extent of the SOMO electron distribution, have a clear correlation with the vertical detachment energy (VDE). When SEM become large, VDE become decreasing. For tetramer and hexamer anions, he also calculates the harmonic vibrational spectra. It is shown that the shifts |ΔνOH|, which are the deviations from the average of two OH modes of free water molecule of the OH bond interacting with the excess electron, which he calls {e}HO bond, in the double proton acceptor water molecules are larger than those of the other {e}HO bonds and |ΔνOH| of hydrogen bonded OH bonds can be larger than those of {e}HO bonds. For hexamer anions, he has shown that the isomer which have two double proton acceptor water molecules and four membered ring structure also have qualitatively similar infrared spectrum with the experimental one.<br /> The water cluster complexes containing a group 1 metal M(H2O)n are another model system for the hydrated electron. The observed ionization threshold energies (ITEs) of M(H2O)n(M = Li, Na and Cs) show several interesting features. Their ITEs are converted at n = 4 and their limiting values are independent of the metal element contained in the cluster. He has studied M(H2O)n(M = Li and Na), for n = 3, 4, 5 and 6 with ab initio MO methods. The optimized geometries and the vertical ionization energies (VIEs) of several isomers for each M and n are obtained at MP2 level of approximation. To characterize the SUMO of the obtained isomers, he has introduced three measures; SEM, R({e}-M) and R({e}-H). R({e}-M) is the distance between the center of the electron (R{e}) and the metal atom. R({e}-H) is a distance between R{e} and the hydrogen atoms. The obtained isomers can be classified into three types (surface, quasi-valence and semi-internal) by SEM and R({e}-M). In the surface type isomers, the electron is distributed on the surface of the cluster. In the quasi-valence isomers, the metal atom is not fully ionized and the SOMO is similar to a diffuse spn hybrid orbital of the metal atom. The isomers of the semi-internal type has an ion pair structure, M+(H2O)m・(H2O)n-m-1・(H2O)1. In the water cluster anion part (H2O)1, there is the OH{e}HO structure. He can interpret the anormalities of the experimental results assuming that the observed isomers are semi-internal type isomers. For the semi-internal type isomers, the VIEs are mainly determined by the local structure of the anion part, (H2O)1, and the electrostatic potential from the hydrated metal cation part, M+(H2O)m. The potential (V SOMO) on the SOMO electron could be written as V SOMO = V SOMO HMI+V SOMO WC, where VSOMO HMI is a long range potential of the M+(H2O)m and V SOMO WC is a short range potential of (H2O)i. He found that V SOMO HMI is almost independent of M and also found that the isomers which have M+(H2O)4 as the hydrated metal cation part are the isomers with lowest VIE. When the cluster becomes large, V SOMO HMI and V SOMO WC change oppositely and cancel each other which results in the constant VIE for n > 4. In the M(H2O)n, OH{e}HO structure has important role to determine the VIE. He has calculated the harmonic vibrational spectra of M(H2O)n for M = Li and Na, n = 3, 4, 5 and 6. In the calculated spectra for the surface type isomers, it is typical that there are the bands which have large intensities and these bands corresponds OH vibrational modes of {e}HO bonds. For quasi-valence type isomers, the frequency shifts I Avon l of {e}HO modes are small. For semi-internal type isomers, the shifts |ΔνOH| of {e}HO modes can be large and comparable to those of hydrogen bonded HO modes. The correlation of the shifts |ΔνOH| with the OH bond lengths R(O-H) for the {e}HO bonds is almost same to that of the hydrogen-bonded OH bonds. The plot of |ΔνOH| against the R(X...H) (X = 0 for hydrogen bond and X = {e} for the interaction between the electron and OH bonds in the OH{e}HO structure), shows that there are two series for {e}HO bonds and |ΔνOH| for {e}HO can be as large as -550 cm-1 which is close to the maximum |ΔνOH| for the hydrogen-bonded OH bond. The data on these two series corresponds to different schemes to interact with the electron. The |ΔνOH| can be treated as a measure of the strength of the interaction between the electron {e} and the OH bonds. There are several features which are similar to those of hydrogen-bonded OH bonds. He calls the interaction between the electron and the surrounding OH bonds the electron-hydrogen bond. The {e}OH bond in the double proton-acceptor water molecules are as strong as hydrogen bonds. The frequency shifts of {e}HO bonds in the double proton-acceptor water molecules are as large as -550 cm-1. | |||||
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| 値 | 有 | |||||
