Theoretical study of nitrogen monoxide adsorption on small Si_x (x = 3–5) clusters

Abstract

Theoretical study of nitrogen monoxide adsorption on small Si _x (x = 3−5) clusters has been carried out using the advanced hybrid meta-density functional method of Truhlar (MPW1B95). MG3 semi-diffuse basis sets were employed to improve the results. The geometry, adsorption energy, natural bond orbital charge, natural population analysis (NPA)-derived spin density and vibrational frequency of NO adsorption on all optimized nanoclusters were investigated. Also using the NPA, we have investigated the change of bond orders through adsorption. It has been found that NO is capable of making n-centre bonds (n = 1−4) from the nitrogen side but bonds to one site from the oxygen end. In the later case the N–O bond order is about 1 and a large value of spin piles up on nitrogen. Adsorption from the nitrogen side is more favoured. Reconstruction of the surface and redistribution of charges towards stable conditions caused large adsorption energies of about −180 kJ mol⁻¹ in some structures. A number of novel structures have been proposed and optimized in this work. Also, exhaustive vibrational frequency analysis was performed to confirm the local minima energy of all optimized structures.

Keywords:

• NO adsorption
• silicon
• DFT
• small cluster

Acknowledgement

We thank Sharif University of Technology for the financial support.