TY - CHAP
T1 - Chapter 19 Characteristics of Chemical Bond in Perovskite-Type Hydrides
AU - Shinzato, Yoshifumi
AU - Komiya, Kenji
AU - Takahashi, Yoshitaka
AU - Yukawa, Hiroshi
AU - Morinaga, Masahiko
AU - Orimo, Shinichi
N1 - Funding Information:
The authors express sincere thanks to the staffs of the Computer Center, Institute for Molecular Science, Okazaki National Institute for the use of super-computers. This study was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan, by the Japan Society for the Promotion of Science, and also by the 21st Century COE program “Nature-Guided Materials Processing”.
PY - 2008
Y1 - 2008
N2 - The electronic structure of typical perovskite-type hydrides, MMgH3 (M=Na, K, Rb), CaNiH3 and SrPdH3, are simulated to understand the nature of the chemical bond between constituent ions in them using the DV-Xα molecular orbital method. For MMgH3, it is found that the valence band consists mainly of the H 1s and Mg 3s, 3p components, and the M s, p components are distributed over the empty conduction band. Thus, the covalent bond still remains between Mg and H ions, but the ionic bond is rather strong between them. The chemical bond between M and H ions is further ionic in character. On the other hand, for CaNiH3 and SrPdH3, covalent bond is dominant between Ni (or Pd) and H ions. Also, the enthalpy change in the dehydrogenation reaction, ΔH, is estimated for several reaction paths, using the plane-wave pseudopotential method. For example, in the NaMgH3 system, ΔH is estimated to be 72.9 kJ/molH2 in the reaction, NaMgH3→NaH+Mg+H2, and 82.6 kJ/molH2 in the reaction, NaH→Na+1/2 H2. In agreement with these calculated results, NaMgH3 dehydrides in these two-step reactions at about 673 K according to recent experiments.
AB - The electronic structure of typical perovskite-type hydrides, MMgH3 (M=Na, K, Rb), CaNiH3 and SrPdH3, are simulated to understand the nature of the chemical bond between constituent ions in them using the DV-Xα molecular orbital method. For MMgH3, it is found that the valence band consists mainly of the H 1s and Mg 3s, 3p components, and the M s, p components are distributed over the empty conduction band. Thus, the covalent bond still remains between Mg and H ions, but the ionic bond is rather strong between them. The chemical bond between M and H ions is further ionic in character. On the other hand, for CaNiH3 and SrPdH3, covalent bond is dominant between Ni (or Pd) and H ions. Also, the enthalpy change in the dehydrogenation reaction, ΔH, is estimated for several reaction paths, using the plane-wave pseudopotential method. For example, in the NaMgH3 system, ΔH is estimated to be 72.9 kJ/molH2 in the reaction, NaMgH3→NaH+Mg+H2, and 82.6 kJ/molH2 in the reaction, NaH→Na+1/2 H2. In agreement with these calculated results, NaMgH3 dehydrides in these two-step reactions at about 673 K according to recent experiments.
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U2 - 10.1016/S0065-3276(07)00019-6
DO - 10.1016/S0065-3276(07)00019-6
M3 - Chapter
AN - SCOPUS:40049107842
SN - 9780123739261
T3 - Advances in Quantum Chemistry
SP - 245
EP - 253
BT - Advances in Quantum Chemistry
A2 - Sabin, John
A2 - Brandas, Erkki
ER -