Calculation Of （MoS₂）_n And （MoSe₂）_n Clusters And Preparation Of Corresponding Films

(MOS2)n and(MoSe2)n clusters are different from corresponding bulk material due to the small size of clusters.However,the(MOS2)n and(MoSe2)n gas-phase clusters can provide specific molecular models.We can obtain possible mechanism about the complicated surface structures and the catalytic processes from well-defined molecular models of(MoS2)n and(MoSe2)n clusters.In order to explore more properties,DFT calculations on(MoS2)n(n ＝1-6)and some(MoSe2)n clusters were systematically studied by using hybrid B3LYP and pure PW91 GGA functions.The stable structures of(MoS2)n and(MoSe2)n clusters were obtained by global optimizations with a genetic algorithm.A triangle of Mo3 capped with a S atom was found to be a favorite building block,which can construct the most stable structures(or at least candidates)for n = 3-6 clusters.This structure can be viewed as fragments of MoS2 monolayer with the 1T phase,which is an important phase with unique reactivity and conductivity properties.Meanwhile,it was also found that although bulk MoS2 is nonmagnetic,the most stable isomers of small(MoS2)n clusters(n = 1-2)are magnetic.In addition,electronic structures were analysed by means of density of states(DOS)and frontier molecular orbitals(FMOs),which suggests that both Mo and S contribute to the FMOs near the Fermi energy while Mo atoms contribute more for unoccupied FMOs.We found that bonding styles of(MoSe2)n clusters are different from(MoS2)n clusters.For(MoSe2)n clusters,Se atoms can easily bond together.But for(MoS2)n clusters.S atoms are not easy to bond together,S and Mo atoms are more willing to bond.In addition,we fabricated monolayer MoS2 and MoSe2 with high crystal quality by chemical vapour deposition,and the surface morphology,structure and optical properties was characterized.