Diffusion Monte Carlo Study of the Small Mixed 3He-4He Clusters

The ground state properties of helium mixed clusters 3He2,3,44He2, 3He2,3,44He3, 3He2,3,44He4, 3He2,34He5, consisting of up to eight helium atoms are studied using variational and diffusion Monte Carlo calculations. For clusters with three and four 3He atoms released-node diffusion Monte Carlo method is used. Our calculations show that, within errorbars, clusters 3He3,44He2 have the same binding energy as the cluster 3He24He2, and that 3He34He3 has the same binding energy as 3He24He3. The clusters 3He3,44He2 and 3He34He3 are in states in which one or two 3He atoms are far away from the rest of the system. Other considered clusters are bound. In particular, we have shown the stability of the cluster 3He44He3, which was previously considered unstable. The calculations are performed using several different interatomic potentials and the conclusions concerning stability are insensitive to the particular form of the interaction potential. We compare our results with the recent experiment and other theoretical calculations.