Competitive shell-filling in protonated helium clusters

The stability steps during the growth of small helium clusters containing a proton charge are examined by performing energy optimization calculations that use a density-functional-based interaction potential. The results obtained for [HenH](+) cluster with It between 5 and 9 are further analysed by carrying out simulated "temperature" annealing dynamics. They clearly reveal that the first helium shell outside the (He2H)(+) ionic moiety is preferentially filled by up to four atoms before the next layer starts being populated and that, when five equatorial atoms are directly bound to the He+ impurity, the latter clusters are found to be markedly less stable than the former ones. (C) 1999 Published by Elsevier Science B.V. All rights reserved.