First-Principles Langevin Molecular Dynamics Studies of Metallic and Semiconductor Clusters: GGA versus LDA Results

Author: Balbás, L.C.

Source: Computing Letters, Volume 3, Numbers 2-4, 2007 , pp. 163-174(12)

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Abstract:

The combination of Langevin molecular dynamics for simulated annealing with realistic quantum-mechanical interactions obtained from first principles supercell calculations within the pseudo potential plane-wave method are applied to examine the structural and electronic properties of the following systems i) pure and mixed Ge_nTe_m (n, m = 0 - 2), Ge₃, Te₃ and Ge₃Te₃ semiconductor clusters, and ii) bimetallic PbNa_n (n ≤ 7) clusters. Results using the local density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange correlation functional are compared with available experimental data. It is found that the GGA leads to larger bond lengths and smaller binding energies than the LDA, but both approximations lead to the same group symmetry for the ground state of these clusters. Two isomeric configurations for PbNa₆, having C_3v and O_h symmetries, respectively, are found. The dipole moments of semiconductor clusters are compared with those estimated from recent experiments at room temperature. The dipole moments from GGA calculations are, on average, in better agreement with experiments than those calculated with the LDA.

Keywords: CLUSTERS; FIRST PRINCIPLES CALCULATIONS; DIPOLE MOMENTS

Document Type: Research article

Affiliations: 1: Departamento de física Teórica, Atómica y Óptica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid, Spain

Publication date: 2007-11-01