Abinitiomolecular dynamics using density-based energy functionals: Application to ground-state geometries of some small clusters

The ground-state geometries of some small clusters have been obtained via ab initio molecular dynamical simulations by employing density-based energy functionals. The approximate kinetic-energy functionals that have been employed are the standard Thomas-Fermi (${\mathit{T}}_{\mathrm{TF}}$) along with the Weizsacker correction ${\mathit{T}}_{\mathit{W}}$ and a combination F(${\mathit{N}}_{\mathit{e}}$)${\mathit{T}}_{\mathrm{TF}}$+${\mathit{T}}_{\mathit{W}}$. It is shown that the functional involving F(${\mathit{N}}_{\mathit{e}}$) gives superior charge densities and bond lengths over the standard functional. Apart from dimers and trimers of Na, Mg, Al, Li, and Si, equilibrium geometries for ${\mathrm{Li}}_{\mathit{n}}$Al, n=1,8 and ${\mathrm{Al}}_{13}$ clusters have also been reported. For all the clusters investigated, the method yields the ground-state geometries with the correct symmetries with bond lengths within 5% when compared with the corresponding results obtained via the full orbital-based Kohn-Sham method. The method is fast and a promising one to study the ground-state geometries of large clusters. © 1996 The American Physical Society.