Small stoichiometric (MoS2)n clusters with the 1T phase

Stoichiometric (MoS2)n clusters (n = 1–6) were systematically studied by density functional theory calculations with hybrid B3LYP and pure GGA PW91 functionals. The most stable structures of these clusters were obtained by global optimizations with a genetic algorithm. A triangle of Mo3 capped with a S atom was found to be a favourite building block, which can construct the most stable structures (or at least candidates) for n = 3–6 clusters. These types of structures can be viewed as fragments of MoS2 monolayer with the 1T phase, which is an important phase that has unique reactivity and conductivity properties. Electronic structures were analyzed by means of density of states and frontier molecular orbitals (FMOs), which suggest that both Mo and S contribute to the FMOs below the Fermi energy while Mo atoms contribute more toward the unoccupied FMOs.