Structural, electronic and vibrational properties of Pb_n S_n (n = 1 - 9) clusters using density-functional theory

The density functional calculation with the generalized gradient approximation is applied to study the structural, electronic and vibrational properties of Pb_nS_n clusters up to n = 9. It is found that ringlike structures are the lowest-energy configuration for n ≤ 3. However, at the beginning of n = 4, three-dimensional spheroid structures are prevailed. The supercluster structures based on Pb₂S₂ and Pb₃S₃ bridges are dominant for the larger Pb_nS_n with n ≥ 3. In addition, we discussed the size dependence of binding energies, gaps between highest-occupied and lowest-unoccupied molecular orbitals, second-order difference of total energies, and the IR spectra of Pb_nS_n clusters. Crown