Electronic structure and magnetism in BeO nanotubes induced by boron, carbon and nitrogen doping, and beryllium and oxygen vacancies inside tube walls

We have performed ob initio calculations to systematically investigate electronic properties and magnetism of insulating non-magnetic beryllium monoxide nanotubes (BeO NTs) induced by nonmagnetic sp impurities: boron, carbon and nitrogen, as well as by nanotube wall defects: Be or 0 vacancies. We found that in the presence of these sp impurities, which replace oxygen atoms, the nonmagnetic BeO NTs transform into magnetic semiconductors, which acquire magnetization caused by spin splitting of (B, C, N) 2p states located in the forbidden gap of a BeO tube. The magnetic moments of the impurities vary from 0.65 to 1.60 mu(B). It was also found that a beryllium vacancy leads to vacancy-induced magnetic moments (at about 0.6 mu(B)) arising on the nearest oxygen atoms and beryllium-deficient BeO nanotubes adopt half-metallic-like properties. On the contrary, when (B, C. N) dopants substitute for Be atoms or in the presence of an oxygen vacancy, the non-magnetic state of the BeO tubes is retained. The results obtained have been compared with theoretically predicted magnetization effects for doped and non-stoichiometric crystalline BeO. (c) 2008 Elsevier B.V. All rights reserved.