Shapes ofHe3clusters

Triaxial deformations are considered for determining the binding energies of open-shell, unpolarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{\mathit{N}}^{}{}_{}{}^{}$ clusters. The shapes of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ clusters are found to be close to spherical, in contrast to the well-deformed shapes of alkali-metal clusters. As a result, odd-even alternations and subshell closures between major shells are absent in the size evolution of the chemical potentials, and the second-energy differences associated with ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{\mathit{N}}^{}{}_{}{}^{}$ clusters. © 1996 The American Physical Society.