Structure, electronic and magnetic properties of (ZnSe)₁₂ clusters doped with one or two Mn atoms were studied with a first-principles method. Substitutional, exohedral, and endohedral doping are considered. Substitutional isomers are found most favorable for both monodoped and bidoped clusters. Magnetic moment is mainly contributed by 3d component of Mn atom, while 4s and 4p orbitals also have certain contributions. Due to hybridization interaction, a small magnetic moment is induced in nearest neighboring Se and Zn atoms. We demonstrate that endohedral bidoped (ZnTe)₁₂ clusters favor ferromagnetic state, which has potential applications in nanoscale quantum devices.

Structural and magnetic properties of (ZnO)₁₂ clusters doped with one (monodoped) and two (bidoped) Ni atoms were studied with a first-principles method. Substitutional, exohedral, and endohedral dopings are considered. Exohedral isomers are found the most favorable for both monodoped and bidoped clusters. Magnetic coupling between Ni atoms at the nearest neighbor position is mainly governed by competition between direct Ni-Ni antiferromagnetic interaction and ferromagnetic interaction between two Ni atoms via O atom due to strong p-d hybridization. Most importantly, exohedral and endohedral bidoped clusters favor ferromagnetic state, which has potential applications in nanoscale quantum devices.

Structural, electronic and magnetic properties of ZnS nanotubes (NTs) doped with Mn atoms are studied with first-principles calculations. Formation energies of doped NTs are smaller than that of the pristine, indicating that doing process is an exothermic reaction. Band gaps of doped NTs are narrower than that of the pristine. It indicates that Mn-doped ZnS NTs tends to adopt antiferromagnetic (AFM) configuration. To obtain room temperature ferromagnetism, we replaced a S atom by a C atom. Ferromagnetic (FM) states are lower in energy than AFM states by 0.454 eV. Such energy difference implies that room temperature ferromagnetism can be expected in the system.

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.

Magnetic properties of single-wall ZnS nanotubes (NTs) doped with Fe atoms are studied with first-principles calculations.Formation energies of doped NTs are smaller than that of pristine one,which indicating that doping is an exothermic reaction.Monodoped NTs has atom-like magnetic moments mainly due to 3d component of Fe atoms.It indicates that Fe-doped ZnS NTs tend to adopt antiferromagnetic (AFM) configurations.To obtain room temperature ferromagnetism,we replaced an S atom by a C atom and found that C atom prefers to substitute S atom connecting two Fe atoms.Ferromagnetic (FM) state energy is lower than that of AFM state by 164 meV.It implies that room temperature ferromagnetism is expected in these systems.

We study systematically structural and electronic properties of ZnO/ZnS superlattice nanowires and core-shell structural ZnO/ZnS nanowires with first-principles calculations. Relaxed structures of these heterostructural nanowires are found similar to those of homogeneous ZnO and ZnS nanowires. Band structures of heteronanowires show that they are direct-band gap semiconductors. For ZnO/ZnS superlattice nanowires, bands become flatter with the formation of minibands. For core-chell ZnO/ZnS nanowires, PDOS show that they are type-Ⅱ heterostructures. These may be important in understanding structural and electronic properties of heterostructural nanowires and their utilization in electric generator and photovoltaic devices.

Structure and magnetic properties of (ZnO)₁₂ clusters doped with one (monodoped) and two (bidoped) Co atoms are studied with first-principles method. Substitutional, exohedral, and endohedral doping are considered. Exohedral isomers are found the most favorable in both monodoped and bidoped clusters. Magnetic coupling between Co atoms is short-range. Magnetic coupling between Co atoms at the nearest neighbor is mainly governed by competition between direct Co-Co antiferromagnetic interaction and ferromagnetic interaction between two Co atoms via O atom due to strong p-d hybridization. We demonstrate that exohedral bidoped cluster favors ferromagnetic state, which has potential applications in nanoscale quantum devices.

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.

Structure and stability of medium-sized (ZnS)_n (n=24,28,36,and 48) clusters are investigated by using first-principles approaches.A number of starting configurations for structural motifs were generated from handmade construction with chemical intuition and cut from bulk crystal.They are optimized via density functional theory(DFT).For medium-sized ZnS clusters,cage and tube structures were found the most preferred structural motifs.With increasing size,onion-like structures became more and more stable,which indicating that they are the lowest-energy structures for larger-sized clusters.Furthermore,it shows that WZ bulklike structures are more stable than ZB bulklike structures in medium-sized ZnS clusters.