Electron-densitiy distributions in transition-metal compounds-Observation by short wave-length SR.
| Project/Area Number |
02044051
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
MARUMO Fumiyuki Tokyo Institute of Technology, 工業材料研究所, 教授 (10013492)
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| Co-Investigator(Kenkyū-buntansha) |
SPADACCINI Nick University of Western Australia, 結晶学センター, 講師
HALL S.R. 西オーストラリア大学, 結晶学センター, 助教授
MASLEN E.N. 西オーストラリア大学, 結晶学センター, 教授
ISHIZAWA Nobuo Tokyo Institute of Technology, 工業材料研究所, 助教授 (90151365)
ITO Tetsuzo Kanagawa Institute of Technology, 工学部, 教授 (60087400)
OHSUMI Kazumasa Laboratory for High Energy Physics, 放射光実験施設, 助教授 (70011715)
SATOW Yoshinori University of Tokyo, 薬学部, 教授 (30150014)
HALL Sydney R. University of Western Australia
MASALEN Edward N. University of Western Australia
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| Project Period (FY) |
1990 – 1991
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| Project Status |
Completed (Fiscal Year 1991)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 1991: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1990: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Keywords | Electron-Density Distribution / Transition Metal Compounds / Short Wavelength / Synchrotron Radiation / Extinction Correction / Perovskite-type Compounds / 単結晶構造解析 / 積分強度 / X線回折 / 放射光 / ペロブスカイト型構造 / 温度因子 / 超伝導 |
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| Research Abstract |
This project has been undertaken as an international joint program between Japanese and Australian crystallographers for the purpose of solving various experimental problems posed on an attempt to develop the X-ray diffraction technique to an promising analytical method for precise electron-distribution analysis in crystals. The primary concern was on establishment of a technique to remove the secondary extinction effects on the integrated intensities of X-rays diffracted from crystals by making use of short wavelength synchrotron radiations (SR). The obtained results can be summarized as follows :
Integrated intensities of a spherically-shaped FeTiO_3 crystal with diameter of 145mum have been collected on a horizontal-type four circle diffractomator at the beam line 14A in the Photon Factory of the National Laboratory for High Energy Physics, Japan. Synchrotron radiations, emitted from the vertical wiggler and monochromatized to 0.34965(5) and 0.41996(14)* using an Si double-crystal mo
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nochromator, were employed for the data collection. Similar measurements were also carried out on the same crystal using AgKalpha (0.56087, *) and MoKalpha (0.71073*) radiations. The effect of secondary extinction on the diffraction data has been examined using these data sets taken with the four different wavelengths. It was revealed that the difference between the observed structure factors before and after the extinction correction was less than 4% at maximum in the 0.35* SR data, indicating that the extinction correction might be practically negligible for the data collected with X-rays of wavelength shorter than 0.3*. In the overall accuracy, however, the 0.35, * SR data were worse those taken with Mo Kalpha radiation because of the instability of the incident SR beam and enlarged errors in counting statistics of the diffracted beams due to the low fraction of the incident beam. The instability is supposed to be mainly caused by a steep drop of intensity against shortening of the wavelength in the case of SR emitted from the vertical wiggler in the wavelength region shorter than around 0.5*. In conclusion, it was suggested to use smaller crystals in combination with a strong and stable SR having a wavelength between 0.5 and 0.9* in place of a SR with a short wavelength such as 0.35* in order to avoid secondary extinction effects. Successful results have been obtained on crystals of K_2SiF_6 and KZnF_3 with dimensions of about 30mum in diameter, utilizing 0.7* SR. In addition, precise analyses of SR data from small crystals of KCuF_3, SrTiO_3, BaTiO_3 and La_<1.88>Sr_<0.12>CuO_4, which were obtained in almost extinction-free conditions, are now in progress and expected to give fruitful. results with respect to their electron-density distributions. Less
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Report
(2 results)
Research Products
(6 results)
