Electronic state and molecular rotation infullerene solid and related compounds

富勒烯分子有望在固体中表现出较大的分子旋转幅度。这种分子旋转能够影响固体中的电子态并导致多种相变。本研究的目的是利用核磁共振技术阐明富勒烯在固体中的分子动力学。主要研究结果总结如下：用核磁共振研究了固体C60、C70和C76的分子动力学和相变。特别是，我们发现固体C76在135-170 K附近发生了与C76分子旋转有关的跃迁。这个温度远低于固体C60和C70.2的温度。采用核磁共振法研究了超导体Na2AC60 （A=K,Rb, Cs）的电子态和分子动力学。我们发现Na2AC60在室温以上是金属塑性晶体。在塑性相中，观察到非常大的13C-NMR自旋晶格弛豫速率，表明存在异常金属态。利用13C-NMR对高压加热制备的C60聚合物和硬碳进行了研究，明确了晶体中存在sp2和sp3碳，并确定了C60的分子旋转。利用核磁共振研究了氨化C60超导体晶体中C60和NH3的分子旋转及其对电子态的影响。

Fullerene molecules are expected to show large amplitude molecular rotation in solid. Such molecular rotation is able to affect the electronic states and lead to variety phase transitions in solid. The aim of the present study is to clarify the molecular dynamics of fullerene in solids by NMR technique. The main results are summarized as follows.1.The molecular dynamics and phase transition in solid C60, C70, and C76 were studied by NMR.Especially, we found that solid C76 shows a transition around 135-170 K related to C76 molecular rotation. This temperature is much lower than those of solid C60 and C70.2.Superconductors, Na2AC60 (A=K,Rb, Cs), were studied by NMR to obtain information on both the electronic state and C60 molecular dynamics. We found that Na2AC60 is metallic plastic crystal above room temperature. In the plastic phase, very large 13C-NMR spin lattice relaxation rate was observed, suggesting an anomalous metallic state.3.C60 polymer and hard carbon prepared by heating under high pressure were studied by 13C-NMR,which clarify the presence of sp2 and sp3 carbons and C60 molecular rotation in crystal.4.Ammoniated C60 superconductors were studied by NMR to clarify the C60 and NH3 molecular rotation in crystal and its effect on the electronic state.