STABILITIES OF SMALL BEN AND BN CLUSTERS (4-LESS-THAN-OR-EQUAL-TO-N-LESS-THAN-OR-EQUAL-TO-8) BY VIBRATIONAL ANALYSIS

The stabilities Be(n) and B(n) clusters (4 less-than-or-equal-to n less-than-or-equal-to 8) based on the vibrational analysis were investigated by ab initio MO calculations. The computations were performed by using a 3-21G basis set at the R(U)HF level and at the R(U)MP4 level with the HF optimized structures. Spin-multiplicities were also considered up to quintet states (n less-than-or-equal-to 7). Of the 120 species that were treated, half of them were considered stable and some of these stable species were obtained by the deformations of transition state and unstable species, following the imaginary normal modes. The transformation barrier between the transition state species and corresponding stable ones was presented. It was found that there were two types of stable clusters: (1) a low symmetry species with lower frequencies and lower geometrical change barriers and (2) a high symmetry one with higher frequencies. The former type was considered as a structural "soft" species and the latter as a "hard" species.