Vibrational frequency and chemisorption site: a DFT-periodic study of NO on Pd (111) and Rh (111) surfaces

Periodic density-functional calculations have been performed to evaluate NO stretching frequencies, for the chemisorption of NO on Pd and Rh (111) surfaces at three different coverages. The threefold fcc and hcp hollow sites are the most stable. The calculated frequency ranges for these sites (1544–1643 cm−1) agree with the HREELS and IR vibrational frequencies, in contrast with the usual assignment to a bridge adsorption. The NO stretching frequency shifts up with increase in coverage. The results suggest that the structural determination from the vibrational analysis using the frequency ranges of nitrosyl complexes could lead to incorrect assignments.