Tham khảo tài liệu 'carbon nanotubes episode 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | METAL-COATED FULLERENES u. Zimmermann N. Malinowski a. Burkhardt and T. p. Martin Max-Planck-lnstitut fur Festkorperforschung Heisenbergstr. 1 70569 Stuttgart Germany Received 24 October 1994 accepted 10 February 1995 Abstract Clusters of C60 and C-ỊỊỊ coated with alkali or alkaline earth metals are investigated using photoionization time-of-flight mass spectrometry. Intensity anomalies in the mass spectra of clusters with composition and C70MA. x 0. . .500 WẼ Ca Sr BaỊ seem to be caused by the completion of distinct metal layers around a central fullerene molecule. The first layer around C60 or C70 contains 32 or 37 atoms respectively equal to the number of carbon rings constituting the fullerene cage. Unlike the alkaline earth metal-coated fullerenes the electronic rather than the geometric configuration seems to be the factor determining the stability of clusters with composition C60 nMA. and C7o nMx M z Li Na K Rb Cs . The units C60M6 and C7OM6 are found to be particularly stable building blocks of the clusters. At higher alkali metal coverage metal-metal bonding and an electronic shell structure appear. An exception was found for C60Lil2 which is very stable independently of charge. Semiempirical quantum chemical calculations support that the geometric arrangement of atoms is responsible for the stability in this case. Key Words Fullerenes mass spectrometry clusters electronic shells icosahedral layers. 1. INTRODUCTION In their bulk intercalation phase compounds of C60 and alkali or alkaline earth metals have been studied intensively spurred particularly by the discovery of superconductivity in several of these metal fullerides such as C60K3 C60Rb3 CS0Ca5 etc. l 5Ị. However despite the wealth of information that could yet be extracted from these fullerene compounds we would still like to return briefly to looking at some interesting experiments that can be done by bringing just one single fullerene molecule in contact with atoms of the metals commonly used for
