Theoretical study on polarities and spectrum properties of WnNim (n+m=8) clusters

The possible equilibrium geometries of WnNim (n+m=8) clusters are optimized by using the density functional theory at the B3LYP/LANL2DZ level. For the ground state structures, the dipole moment, polarizability and vibrational spectrum are analyzed. The calculated results show that each of all the clusters of WnNim (n+m=8) has a polarity, and W-rich clusters which have a strong nonlinear optical effect each and are easy to be polarized by external electromagnetic field, that vibrational frequencies are mainly distributed in a 0–350 cm-1 range, but the cluster of W4Ni4, due to the particularity of vibration mode, has a obviously strong peak on IR spectrum and also on Raman spectrum, each at a frequency of 421.971 cm-1, and that the W5Ni3 cluster, with high symmetry of C3v point group, presents a resonance phenomenon on IR spectrum.