Independent determination of the temperature factor of each atom in a powder sample of diatomic crystals
Project/Area Number  04680057 
Research Category 
GrantinAid for Scientific Research (C).

Allocation Type  Singleyear Grants 
Research Institution  Nihon University 
Principal Investigator 
UNO Ryosei College of Humanities and Sciences, Nihon University, Applied Physics, Professor, 文理学部, 教授 (00058661)

CoInvestigator(Kenkyūbuntansha) 
ISHIHARA Nobukazu College of Humanities and Sciences Nihon University, Applied Physics, Assistant, 文理学部, 助教授 (30059167)

Project Period (FY) 
1992

Project Status 
Completed(Fiscal Year 1992)

Keywords  Xray powder diffraction / Anomalous scattering / Temperature factor / diatomic crystals / Semiconductors 
Research Abstract 
We adopted GaAs as an typical material of twoatomic crystals and tried an independent determination of the temperature factor of Ga atom in a powder sample. This project was started in 1988 with a GrantinAid for Scientific Research (B) and we applied for the grant to improve the accuracy of measurement of diffraction intensity. We have carried out diffraction measurements at 2 pairs of wavelengths on the longer and shorter wavelength sides of Kabsorption edge(1.19580A) of Ga atom and at 2 wavelengths on the longer wavelength side, at the Photon Factory of the National Laboratories for High Energy Physics, this year. After the reception of the grant we could have only one machine time when we carried out diffraction measurements at 1.19857 and 1.19332 A. We can get the temperature factor of 3.5A^2 from the pairs of measurements at longer and shorter sides of the Kedge, which contains much error refering to atomic distance of 2.45A and also compared with the factor 0.916A^2 obtained at Cuk alpha 1 by means of the conventional method, mainly because of low accuracy at the shorter wavelength side. Since the accuracy of measurements at longer wavelength side is comparatively high, the temperature factor was estimated from fairs at longer side where difference in f'_G is enough to estimate the temperature factor of Ga and the difference in f"_G can be neglected. In this method the atomic scattering factor of Ga is necessary and the obtained value was 1.3A^2, which is also larger than 0.916A^2. However, f'_G and f"_G are calculated from contributions of K and L electrons, so that the factor 1.3A^2 corresponds to the vibration of the ion core, whereas 0.916A^2 corresponds to the vibration of atom as a whole under the assumption of a rigid atom. The real Ga atom is not so rigid that the vibration of the ion core can be larger than that of the whole atom. The result of 1.3 A^2 may be reasonable and can be the result of vibration of the ion core.

Report
(2results)
Research Output
(3results)