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Investigation on the silicon network solids and related materials

硅网络固体及相关材料的研究

基本信息

批准号：
11165232
负责人：
MANIWA Yutaka
金额：
$ 16.96万
依托单位：
Tokyo Metropolitan University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas (A)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

We investigated silicon network solids and related materials, and obtained the following results.(1) Silicon clathrate superconductor, Ba_8Si_<46> was found to show anomalous behaviors of spin-spin relaxation rate 1/T_2 and Knight shift in the superconducting state.(2) It was confirmed that the sharp large peak of the electronic density of states at the Fermi level is responsible for the occurrence of superconductivity in Si_<46> superconductors. The peak is due to a hybridization between Si and Ba orbitals.(3) A_3C_<60> compounds with large and small lattice constants, such as (NH_3)A_3C_<60>, Na_2AC_<60> and Li_xAC_<60> where A is alkali metals, were systematically investigated by NMR. The t_<1u> orbital degeneracy is important for the stability of the metallic states, and that its splitting and orbital ordering lead to antiferromagnetic ground states.(4) A new layered superconductor, HfNCl, was investigated by NMR and magnetic susceptibility. It was found that HfNCl is a two-dimensional superconductor with a very small density of states at the Fermi level. It was suggested that the superconductivity cannot be explained by the conventional mechanisms.(5) Thermal expansion of MWNT and SWNT was determined by means of x-ray diffraction. MWNT sample grown in hydrogen atmosphere was found to contain a lot of closed Russian doll type tubes for the first time.(6) C_<60> Polymers including Li and Na were investigated by NMR. It was shown that there are sp^3 carbon atoms consistent with proposed structures, and that the alkali ions are moving in the crystals.(7) Alkali-loaded zeolite LTA, whose framework structure is similar to that of the Si46 clathrates, was studied by NMR to clarify the origin of the ferromagnetism at low temperature in this system. The ^<29>Si NMR gave us information on the distribution of the magnetic moments.

我们对硅网络固体及相关材料进行了研究，得到了以下结果：(1)包层硅超导体Ba8Si46&gt；在超导态表现出自旋-自旋弛豫速率1/T2和奈特漂移的反常行为.(2)证实了在费米能级电子密度的尖峰是导致超导体超导的原因.(3)用核磁共振方法系统地研究了(NH_3)A_3C_&lt；60&gt；(NH_3)A_3C_&lt；60&gt；，Na_2AC_&lt；60&gt；和Li_xAC_&lt；60&gt；等具有大小晶格常数的化合物。T&lt；1u&gt；轨道简并对金属态的稳定性很重要，它的分裂和轨道有序性导致了反铁磁基态。(4)用核磁共振和磁化率研究了一种新型层状超导体HfNCl。研究发现，HfNCl是一种二维超导体，在费米能级上具有很小的态密度。用X射线衍射法测定了碳纳米管和碳纳米管的热膨胀系数。首次发现在氢气气氛中生长的多壁碳纳米管样品中含有大量的封闭的俄罗斯洋娃娃形管。(6)用核磁共振研究了包括Li和Na在内的C&lt；60&gt；聚合物。(7)用核磁共振方法研究了骨架结构与Si46笼状结构相似的含碱LTA分子筛的结构，阐明了该体系低温铁磁性的来源。核磁共振给出了磁矩分布的信息。