Structure, stability and electronic properties of composite Mo1-xNbxS2 nanotubes

The effect of Mo -> Nb substitution on the electronic structure of MoS2 nanotubes has been investigated using the density functional tight binding method (DFTB). It has been found that composite Mo1-xNbxS2 nanotubes (with Nb contents of 5, 10 and 25 at%) are more stable than the corresponding pure tubes, especially for larger tube diameters. The defect-formation energy indicates that the most stable dopant arrangement is a NbS2 stripe along the tube direction. However, entropy effects may favor a random arrangement of Nb dopant atoms at high temperatures in the tubes with a larger diameter. All of the studied Mo1-xNbxS2 nanotubes have metallic properties, independent of their chirality, diameters and ordering type of substitutional atoms. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheirn