Structure growth, stability and adsorption properties of (AgZn3)n clusters.

Recently, an effective syngas catalyst composed of AgZn3 clusters is reported, in which the CO and H2 generation may occur at the Zn sites and the hollow sites between Ag and Zn. Hence, the atomic model of the AgZn3 is worth established to further investigate the catalytic mechanism. Here, we take advantage of the genetic algorithm with the density functional theory to unbiasedly search configurations of (AgZn3)n (n = 1–6) clusters. It is found that (AgZn3)n clusters evolve from hollow cages to close-packed structures, with Zn atoms gradually occupying the core positions. The Eb and Δ2E analyses show that the (AgZn3)3 has a higher stability than that of its neighbors. The AIMD simulations demonstrate that the (AgZn3)3 shows a favorable stability at 700 K. The molecular orbitals reveal that 21 valence electrons of the (AgZn3)3 fill superatomic orbits resulting in an electronic configuration of 1S21P61D102S21F1. The adsorptions of CO on the bridge sites of (AgZn3)3 are much higher in energy than the top adsorptions, but the red shift of the stretching frequency of C-O is more obvious in the former. Our results are verified that the Zn sites and bridge sites between Ag and Zn are active sites for CO. [ABSTRACT FROM AUTHOR]