Structure, stability and electronic properties of composite Mo _1-xNb_xS₂ 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 Mo _1-xNb_xS₂ 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 Mo_1-xNb_xS₂ nanotubes have metallic properties, independent of their chirality, diameters and ordering type of substitutional atoms.