Thermodynamic study of nanoclusters of lead (Pbn, n=1-8): Adsorption of small molecules on the Pbn clusters

Lead (Pb) is a toxic metal which can damage various systems and tissue of the body and affect human health. Although atmospheric concentration of lead has been decreased by removing tetraethyl-lead (PbEt4) from gasoline, lead pollution is widespread due to its wide industrial uses. In this work, nano clusters of lead (Pbn, n=1-8) were studied theoretically employing MP2 and M062X methods. Structural and thermodynamic properties as well as ionization energies (IE) and electron affinities (EA) of two isomers of Pb3, six isomers of Pb4, seven isomers of Pb5 and seven isomers of Pb6 were obtained at 298 K. Using the IE and EA values, the hardness and electronegativity data were computed for the Pbn clusters. Rhombic, pyramidal and octagonal structures were the most stable forms of the Pb4, Pb5 and Pb6 clusters, respectively. Adsorption of C2H2, C2H4, CO, CO2, CH2O, HNO, O3, NO, N2O, NO2, N2O4 and N2O5 on the Pbn clusters was studied. O3 showed the strongest interaction with the Pbn clusters with adsorption enthalpies of 80-130 kcal/mol. HNO, O3, N2O, N2O4 and N2O5 were dissociated after adsorption on the Pbn clusters. N2O decomposes to adsorbed O atom and a free N2 molecule while N2O4 and N2O5 release NO2 molecule. Effect of Pbn clusters on the energies of the C-H, O-H and N-H bonds of some adsorbed molecules was investigated. It was found that, in most cases, adsorption causes weakening of the bonds.

Keywords:

Pbn cluster , Ionization energy , Adsorption , Ozone