New Material Development by Metal Doping and Electronic Properties for Boron-rich Solids having Icosahedron and Soccer-ball Clusters

1)通过分子轨道计算的结合能计算，发现富硼体系中理论上存在α -菱面体硼型准晶，并预测硼碳体系中准晶结构的组成范围小于9at。通过计算结果和晶体学数据。在非晶相退火后，我们发现了一种新型的二十面体准晶近似相。这一发现表明，在富硼固体中实现半导体准晶体是非常有希望的，这是实现半导体准晶体的有价值的第一步。2)利用石英和钽构成的双密封管，成功地将Li掺杂到β -菱面体硼（β -硼）中。用同样的方法，我们尝试制备了锂掺杂的菱面体硼，并通过能带结构计算预测其为超导体。3)我们指出了β -硼与氟氯化碳（氟氯化碳<60>）之间的结构相似性，因为β -硼也由位于菱面体单元胞每个顶点的足球团簇组成。多达几个小时。Li或Cu掺杂的导电率仍然表现出半导体的特征，磁化率仍然是抗磁性的。这些行为与C_<60>时不同。根据电导率显示变范围跳变型电导率和磁化率对掺杂几乎保持不变的结果，我们认为掺杂β -硼的电子结构如下：而掺杂电子占据了源自B_<12>簇的本然受体能级，并在局域能级之间跳跃，由于电子-声子相互作用，有效电子-电子相互作用为负。4)我们测量了β -硼的光吸收边缘光谱的温度依赖性，证实了从本征受体能级到导带的电子跃迁是被禁止的。这与偶极矩计算是一致的。我们首次成功地测量了光致发光光谱。从峰值能量和温度对强度的依赖性来看，我们得出了发光对应于本征受体能级的空穴与最高俘获能级的电子之间的复合。少

1) From cohesive energy calculations using molecular orbital calculation, we found that alpha-rhombohedral boron type quasicrystal can be exist theoretically in boron-rich systems, and predict that the composition range for the quasicrystalline structure in boron-carbon system is less than 9at.% carbon by accounting the results and crystallographic data. In the composition range, we discovered a new type of approximant phase of an icosahedral quasicrystal after annealing amorphous phase. This discovery suggests that realization of semiconducting quasicrystal in boron-rich solids is strongly expected and this is a valuable first step for the realization. 2) We succeeded in Li doping into beta-rhombohedral boron (beta-boron) using double-sealed tube constituted by quartz and tantalum. By the same method, we have tried to prepare Li-doped alpha-rhombohedral boron which is predicted to be a superconductor by energy band structure calculation. 3) We pointed out the structural similarity bet … More ween beta-boron and f.c.c.C_<60> because beta-boron also consists of soccer ball clusters located at each vertex of a rhombohedral unit cell. Up to several at.% of Li or Cu doping electrical conductivity still exhibited characteristic feature of that of semiconductor and magnetic susceptibility was still diamagnetic. These behaviors are different from those in the case of C_<60>. On the basis of the results that electrical conductivity reveals variable range hopping type conduction and magnetic susceptibility remain almost constant against the doping, we consider the electronic structure of the doped beta-boron as follows ; whereas the doped electrons occupy the intrinsic acceptor levels originated from B_<12> cluster and they jump between the localized levels, effective electron-electron interaction is negative due to electron-phonon interaction. 4) We measured the temperature dependence of optical absorption edge spectrum for beta-boron, and confirmed that the electronic transition from the intrinsic acceptor level to the conduction band is forbidden. This is consistent with the dipole moment calculation. We succeeded in measuring photoluminescence spectrum for the first time. From the peak energy and the temperature dependence of the intensity, we concluded that the luminescence corresponds to recombination between a hole in the intrinsic acceptor level and an electron in the highest trapping level. Less