Lattice Location and Density Distribution of Hydrogen in [Beta]^sub 1^-V^sub 2^H

• Published in: Journal of the Physical Society of Japan 2012-04, Vol.81 (4), p.1
• Main Authors: Yagi, Eiichi, Hayashi, Tatuya, Yoshida, Toru, Koike, Shigetoshi, Higami, Naota, Hirabayashi, Kazuhiro, Takebayashi, Akiko, Matsuba, Hiroshi, Ogiwara, Kiyoshi
• Format: Article
• Language: English
• Subjects: Diffraction; Hydrogen; Normal distribution; Single crystals; Tensile strength
• ISSN: 0031-9015; 1347-4073

The lattice location of hydrogen and its spatial density distribution in the tetragonal β 1 -V 2 H single crystal prepared under tensile stress and the monoclinic β 1 -V 2 H 1.1 single crystal prepared without application of tensile stress have been studied at room temperature by the channelling method utilizing a nuclear reaction 1 H( 11 B,a)aa with a 11 B beam of about 2 MeV. In these crystals, H atoms are located at octahedral ( O ) sites with different distributions over O x , O y , and O z sites. In the tetragonal β 1 -V 2 H, about 80% of H atoms are located at O z sites, about 10% of them at O y sites and about 10% of them at O x sites. In the monoclinic β 1 -V 2 H 1.1 , about 65% of H atoms are located at O z sites, about 20% of them at O y sites and about 15% of them at O x sites. These results support the theoretical prediction that hydrogen preferentially occupies O z sites under tensile stress along the z -axis ( c -axis). In both crystals, the HWHM of the spatial density distribution of hydrogen is about 0.35 A in the [100] direction, whereas it is less than 0.13 A in the [001] direction on the assumption of the Gaussian distribution. The HWHM in the [110] direction has been measured only in the tetragonal crystal to be about 0.35 A. These values are much smaller than those hitherto obtained by the neutron diffraction method, and close to the values theoretically calculated for the ground state.