ИСТИНА

Since the very discovery carbon nanotubes attracted interest of scientists thanks to the vast perspectives of their application. According to the concrete ways of rolling up, these structures unexpectedly display a wide variety of properties, including magnetic [1]. The principal aim of this work was to investigate magnetic properties of single-walled carbon nanotube fragments with zigzag-shaped edges (n, 0). In order to compare results of this work and of the main article [2] and to observe regularity of properties, it was suggested to examine finite carbon nanotubes (8, 0) with fragments as long as q = 3, 4, 5. With reference to the main article of comparison a structure with the dehydrogenated zigzag edge (DHZE) at one end and the mono-hydrogenated zigzag edge (MHZE) at the other end was created. For the electronic structure calculation, we used the same B3LYP functional, basis set 6-31G* as in the article [3]. All the theoretical calculations were performed with PC GAMESS [4]. All the structures were optimized. Two main schemes of spin coupling were calculated. High-spin scheme (ferromagnetic properties) resulted much lower on the energetic scale than the low--spin variant. Low-spin model correlates with antiferromagnetic properties; in the literature this type of solutions is called the Broken-Symmetry. Furthermore, the energetic differences between the investigated spin states were analyzed. The results obtained in this work contrast sharply with [2], where LSDA functional was used. An assumption was allowed that such calculation procedure may depend on the type of the exchange-correlation functional. True results can not be yielded using functionals not advanced enough. Nano-scaled magnetic materials based on suggested structures are extremely promising. This work was supported by RFBR (grant ���� 10-03-00665).