A.О. Litinskiy, V.V. Kamnev

The cyclical cluster model and the density functional theory method were applied to the investigation of the electron energetic structure of double-walled carbon nanotubes both doped with alkaline metal (Li, Na, K) atoms in the inter-wall space, and without defects. The Perdew-Burke-Ernzerhof-s exchange-correlation potential in the valent double exponential basis set of pseudo-atomic orbitals was used. The core-electrons influence was taken into account by Troullier-Martins - pseudopotential introduction in the Kleinman-Bylander-s form. It was shown that in a case of inter-wall distances of an order of values taking place in the corresponding graphite intercalated compounds, alkaline metal atoms have one stable state(single-well potential), in a case big distances they have two stable states (double-well potential). The introduction of alkaline metal atoms into an inter-wall space is energetically favourable in both cases (the energy gain is ~5,8÷5,9 eV for Li and Na; ~6,7 eV for K). With increasing of an external tube diameter for ideal structures the Fermi-s level position almost isn-t changed in a case of the single-well potential and is incremented a little in a case of the double-well potential. When inculcating corresponding alkaline metal atoms into an inter-wall space the structure gets a metallic conductivity (the forbidden energy gap disappears), their Fermi-s level decreases from Li to Na and K, and Fermi-s level shift increases in this series relatively the ideal structure. When the alkaline metal atom is being moved from the nearest to an inner tube minimum towards the nearest external tube minimum it is necessary to overcome the U1 = 0,24; 0,12; 0,09 eV barrier and U2 = 0,08; 0,06; 0,07 eV in the opposite direction (for Li, Na and K correspondingly). When alkaline metal atom is moved in such a way the electronic density redistribution between alkaline metal atoms and external and inner tubes takes place, and the electronic density is always transferred from alkaline metal atoms to carbon tubes atoms. Estimations of voltages values necessary to apply between inner and external tubes to convert the system (to throw over alkaline metal atom) from one stable state into another were made. They have the same order as working voltages for various microelectronic devices. The conclusion was made that the nanosystems with two stable equilibrium states could find application in corresponding micro - and nanoelectronic devices.