Ab initio molecular dynamics using density based energy functionals: application to ground state geometries of some small clusters

TL;DR

This paper demonstrates that density functional-based ab initio molecular dynamics can accurately predict ground state geometries of small clusters, offering a faster alternative to traditional orbital-based methods.

Contribution

It introduces a density functional approach with improved kinetic energy functionals for efficient ground state geometry determination of small clusters.

Findings

Functional with F(N_e) yields better charge densities and bond lengths.

Method achieves bond length accuracy within 5% of Kohn-Sham results.

Approach is fast and suitable for large cluster studies.

Abstract

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 $(T_{TF})$ along with the Weizsacker correction $T_W$ and a combination $F(N_e)T_{TF} + T_W$. It is shown that the functional involving $F(N_e)$ gives superior charge densities and bondlengths over the standard functional. Apart from dimers and trimers of Na, Mg, Al, Li, Si, equilibrium geometries for $Li_nAl, n=1,8$ and $Al_{13}$ clusters have also been reported. For all the clusters investigated, the method yields the ground state geometries with the correct symmetries with bondlengths within 5\% when compared with the corresponding results obtained via full orbital based Kohn-Sham method. The method is fast and a promising one to study the ground state geometries of large clusters.