Adsorption Behaviour of Sarin on Zn12O12 and Cu12O12 Nanoclusters: A Theoretical Study Based on DFT Approach

Here we present adsorption and decomposition behaviour of sarin, a nerve gas molecule, on Zn12O12 and Cu12O12 cluster, as representative model for ZnO and CuO surface, using DFT formalism. LCAO-MO based approach has been adopted in the present study. For both the cluster systems investigated, sarin is found to interact with these clusters via dative bond involving lone-pair of phosphoryl oxygen as donor and Zn/Cu atom as acceptor. Sarin is found to undergo decomposition on these clusters via dissociation of O–isopropyl bond. The intrinsic reaction coordinate (IRC) analysis was performed for characterizing the transition states associated with decomposition of adsorbed sarin on Zn12O12 and Cu12O12 clusters. Gibbs free energy of activation (ΔGǂ) for decomposition of sarin is estimated to be 31.62 and 28.30 kcal/mol, for Zn12O12 and Cu12O12 clusters respectively. Our studies indicate that though decomposition of sarin on these substrates is thermodynamically favourable, the reaction rate of sarin decomposition is slow at room temperature. Thus implying requirement of higher temperature for the decomposition reaction, to be kinetically feasible.