| Περίληψη: | The many-body expansion (MBE) was applied to homometallic and heterometallic trimers of metals with ns1, ns2, and ns2p1 configurations to investigate its convergence, the magnitude and nature (stabilizing/destabilizing) of the individual terms and seek an understanding of their variation across the different families of clusters. In particular, we examined the series of alkali metals (Li3, Na3, K3, Li2Na, LiNa2), alkali metal borides (Li2B and LiB2), and alkaline earth metals (Be3, Be2Mg, BeMg3, and Mg3) trimers, as well as sodium clusters Nan, n = 2-5. We found that there is no uniform contribution (stabilizing or destabilizing) across the series in the different families of trimers. For instance, the 2-B term stabilizes the ground states of the Na3 (doublet), Na4 (singlet), and Na5 (doublet) clusters, and the 3-B term destabilizes them; however, the opposite holds for the quartet state of the Li3, Li2Na, LiNa2, and Na3 clusters (destabilizing 2-B, stabilizing 3-B). Substituting Li with B in the quartet state of Li3 results in a significant reduction of the 3-B term amounting to 16% (Li2B) and 5% (LiB3) of the binding energy. On the contrary, the ground states of the alkaline earth metal clusters (Be3, Be2Mg, BeMg3, and Mg3) are stabilized by the 3-B term, while the 2-B term destabilizes them. Overall, we find that the 3-B terms significantly stabilize the high-spin multiplicity states of the ns1 configurations and the low-spin states of the ns2 configurations. Finally, as the size of the metal increases, the contribution of the 3-B term to the binding energy decreases due to the longer metal-metal bond distances. |
