Structures and magnetic properties of Cr monodoped and bidoped single-wall ZnS nanotubes are studied with firstprinciples calculations. Formation energies of doped nanotube are lower than those of pristine ones, indicating that doing process is an exothermic reaction. Doped nanotubes have atom-like magnetic moments mainly due to 3d component of Cr atoms. Our results indicate that Cr-doped ZnS nanotubes tends to adopt ferromagnetic (FM) configuration. Energy differences between FM and antiferrimagnetic (AFM) is only 36 meV. To obtain room temperature ferromagnetism, we replace one S atom by C atom. Its FM states are lower in energy than AFM states by 497 meV. Such large energy differences imply that room temperature ferromagnetism could be expected.

Electronic and magnetic properties of ZnS nanotubes (NTs) were investigated systematically using first-principles approach. A double-wall NT (DWNT) with hexagonal cross section (HCS) shows higher stability, while zigzag and armchair NTs with round cross section (RCS) show lower stability than single-wall NT (SWNT) with HCS. Electronic band structures show that they are direct band gap semiconductors. With hydrogen adsorption, SWNT with HCS transform into indirect band gap semiconductor. Magnetic properties of ZnS NTs doped with transition-metal(TM) atoms (Cr, Mn, Fe, Co, and Ni) are calculated. Formation energies of doped NTs are smaller than those of the pristine ones, indicating that doing process is an exothermic reaction. All NTs have atom-like magnetic moments mainly due to 3d component of the TM atoms. Monodoped NTs have potential utility in materials with tunable magnetic properties.