Structure and Electric Properties of SnN Clusters (N=6-20) from Combined Electric Deflection Experiments and Quantum Theoretical Studies

Electric deflection experiments have been performed on neutral Sn-N clusters (N = 6-20) at different nozzle temperatures in combination with a systematic search for the Global minimum structures and the calculation of the dielectric properties based on density functional theory. For smaller tin clusters (N = 6-11), a good agreement between theory and experiment is found. Taking theoretically predicted moments of inertia and the body fixed dipole moment into account permits a quantitative simulation of the deflected molecular beam profiles. For larger SnN clusters (N = 12-20), distinct differences between theory and experiment arc observed; i.e., the predicted dipole moments from the quantum chemical calculations are significantly larger than the experimental values. The investigation of the electric susceptibilities at different nozzle temperatures indicates that this is due to the dynamical nature of the tin clusters, which increases with cluster size. As a result, even at the smallest nozzle temperature of 40 K, the dipole moments of Sn12-20 are partially quenched. This clearly demonstrates the limits of current electric deflection experiments for structural determination and demonstrates the need for stronger cooling of the clusters in future experiments.