Investigation of the Spin Competition in the Al6 Cluster

Abstract

Small-sized aluminum clusters exhibit a possible spin competition at finite temperatures. For this reason, it is difficult to perform standard electronic structure investigations to determine the properties of the ground states of such clusters. In the particular case of Al6, a nonmagnetic ground state has been predicted at 0 K. However, singlet–triplet intercrossing could occur at laboratory temperatures, in agreement with Stern–Gerlach experiments. We have thus investigated, by means of nonadiabatic transition state theory, the possibility of such singlet–triplet spin competition. We determined the possible crossing points on the potential energy surface and then identified the most favorable minimum-energy crossing points. For these points, we evaluated the spin–orbit matrix elements, transition probabilities, and rate constants for the singlet–triplet equilibria at different temperatures using the Landau–Zener and weak-coupling formulas. The predicted equilibria at finite temperatures are consistent w...