1998 Fiscal Year Final Research Report Summary
Inner displacement and directional bonding in transition metal disilicides
| Project/Area Number |
09650716
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical properties of metals
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
TANAKA Katsushi Dept.Mater.Sci.& Eng.KYOTO UNIVERSITY Research associates, 工学研究科, 助手 (30236575)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Transition metal disilicide / Elastic constants / Structural analysis / Co-valent bonding / Maximum entropy method / Electron density distribution |
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| Research Abstract |
For the first step of this project, we have measured single crystal elastic constants of transition metal disilicides with the C11_b, C40 and C54 structures. The elastic constants have been analyzed by the valence force field approach where the inter-atomic interaction is classified into two terms ; bond-stretching and bond-bending. Relative values of the coefficients of these two terms for each transition metal disilicide indicate the directionality of the inter-atomic bonding. The directionality of inter-atomic interaction in the materials with the C11_b structure is the strongest one, and that in the materials with the C40 structure are classified into two groups. The strength of TiSi_2 is located at the middle position between the two groups of the C40 structure.
For the next step, we have performed the X-ray analysis to refine the crystallographic parameters of these compounds. The analysis indicates that the position of silicon atoms in the materials are slightly displaced from the position compiled in the data book. The displacement is associated with the anisotropic inter-atomic interactions of Si-Si and Si-TM.This is clearly demonstrated from the electron distribution maps which are constructed from the measured intensities of the diffraction by the maximum entropy method.
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