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Investigation of lattice defects in LaNi 5 by positron annihilation spectroscopy and first‐principles calculations
Author(s) -
Mizuno Masataka,
Araki Hideki,
Shirai Yasuharu
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.22080
Subject(s) - vacancy defect , hydrogen , binding energy , positron annihilation spectroscopy , lattice (music) , spectroscopy , atomic physics , positron lifetime spectroscopy , chemistry , positron , absorption spectroscopy , materials science , crystallography , positron annihilation , electron , nuclear physics , physics , organic chemistry , quantum mechanics , acoustics
ositron annihilation spectroscopy and first‐principles calculations have been applied to identify lattice defects introduced in LaNi 5 , which is widely used as hydrogen storage materials, during hydrogen absorption–desorption process. Positron lifetime measurement and calculated positron lifetimes revealed that Ni vacancies are formed during hydrogen absorption in LaNi 5 . First‐principles calculations have been performed in order to estimate the stability of the Ni vacancy in the hydrogen absorption process. The binding energy at the Ni sites is reduced by absorbed hydrogen atoms in LaNi 5 hydrides. In the case of the Ni 2b site surrounded by four hydrogen atoms, the binding energy is lowered by about 0.7 eV. Another contribution to the stability of the Ni vacancy is a decrease in the energy of additional lattice sites occupied by the atoms removed as vacancies. In the hydrogen absorption process, additional hydrogen sites are occupied by hydrogen atoms supplied in the process, which leads to the decrease in the vacancy formation energy. As a result, the formation energy of Ni vacancy is reduced to almost zero in the hydrogen absorption process of LaNi 5 . © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009