| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2004: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2003: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Research Abstract |
The main aim of this research is to study the quasicrystal phase stability of Cu-Ga-Zn-Mg icosahedral phase. It have already been reported that a CuGaZnMg is an P-type icosahedral phase. But the other icosahedral phases are F-type icosahedral. We have made the program of the Huang scattering for icosaheral symmetry crystal. The experimental results o are in the icosahedral phases as follows.
1)The pseudo-gap around the Fermi surface in the Cu-Ga-Zn-Mg icosahedral phase is observed by the UPS study and that in the Ga-Zn approximant is not observed. 2)The depth and width of the gap is 0.6 and 0.2eV, respectively. 3)It is very difficult for the x-ray study to be done. It seems that one of the reason is multi scattering effect is not ignored.
The calculated results of the Huang scattering intensity are in the icosahedral phases as follows.
1)The Huang diffuse distribution around the reflection along the 2-fold axis is elliptic spread toward the transverse direction. 2)The Huang diffuse distri
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bution around the reflection along the 5-fold and 3-fold axis is not elliptic spread toward the transverse direction and like the complex shape. 3)The diffuse scattering intensity distribution of Al-Pd-Mn is symmetrical along the longitudinal direction, but that of Al-Cu-Fe is asymmetric. The reason, called "asymmetrical" in this case, is that the center of the rhombus is notjust on the diffraction point, but is located on the slightly inside. 3)The shape of diffuse intensity contour depends on the intensity. 4)The intensity of the diffuse scattering in Al-Cu-Fe depends little on the temperature below 300K.
Therefore, it is thought that the diffuse scattering is mainly produced by the defects. In the defects, a defect, called a (frozen) "phason" proper to a quasicrystal, is naturally included besides an impurity and/or defect included in a "usual" crystal. The experimental result seems to show the limit of elastic approximation as Huang scattering. The contour of the diffuse scattering intensity cannot individually be explained as every map of Huang scattering, and seems to consist of the sum of all three diffuse scattering components.
As the comparison between experimental and calculation, we can think followings. The major defects in Al-Pd-Mn and Al-Cu-Fe can be exchange-type, which are created by interchange of atoms and/or atomic clusters. However, the concentration of atoms and atomic clusters is unchanged from the ideal structure by this type of defect. Random phason is clearly classified into this type. The type of the defect is similar to the exchange-type but is accompanied by deviation of concentration of atoms and atomic clusters from the ideal state. As the "asymmetrical" cannot be explained with the approximation of Huang scattering, it is probably caused by a size effect. Less
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