Density Functional Study of Structural and Electronic Properties of AlPn (2≤n≥12) Clusters

Low-lying equilibrium geometric structures of AlP (n) (n = 2-12) clusters obtained by an all-electron linear combination of atomic orbital approach, within spin-polarized density functional theory, are reported. The binding energy, dissociation energy, and stability of these clusters are studied within the local spin density approximation (LSDA) and the three-parameter hybrid generalized gradient approximation (GGA) due to Becke-Lee-Yang-Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static dipole polarizabilities are calculated for the ground-state structures within the GGA. It is observed that symmetric structures with the aluminum atom occupying the peripheral position are lowest-energy geometries. And the Al impurity in the most stable structures of AlP (n) clusters can be looked upon as a substitutional impurity in pure P (n+1) clusters or capping Al atom in the different peripheral positions of pure P (n) clusters. Generalized gradient approximation extends bond lengths as compared to the LSDA lengths. The odd-even oscillations in the dissociation energy, the second differences in energy, the HOMO-LUMO gaps, the ionization potential, the electron affinity, and the hardness are more pronounced within the GGA. The stability analysis based on the energies clearly shows the AlP5 and AlP7 clusters to be endowed with special stabilities.