Structure and stability of aluminum Clusters : a molecular dynamics Study with gupta potential

Abstract

In this thesis, we have determined the ground-state geometries and energies of aluminum, A`N(3 · N · 170) clusters. We have developed a classical Molecular dynamics code using the Gupta potential. The Gupta parameters have been fixed according to the experimental values of the cohesive energy and lattice parameters. For each minimum, the energy and Point Group (PG) have been obtained. The optimized structures are in good agreement with previous ones obtained using Murrell-Mottram potential as well as those obtained using the Glue potential. Aluminum clusters have shown some degree of stability through the little fluctuations observed for few clusters with their number of atoms, known as magic numbers which is due to the saturation of electronic orbitals generated by the entire atomic aggregate. A simple relation between the ground state energy and the number of atoms has been proposed which can permit one to predict the ground state for any cluster size with a known number of atoms. We have obtained the cohesion energy of the aluminum crystal with an accuracy of 99:81%. We have shown in our work that the centered cubic structure is not the optimized structure of A`9 as mentioned in the literature. However, it remains an isomer because its energy is 2.0318 eV greater than that of the optimized structure obtained in this work. Finally, we have obtained with the best precision (98:13%), the distance between the two aluminum atoms of the A`2 dimer .