The origin of the shift in the CO vibration of chemisorbed CO: Cluster model studies for CO / Cu(100)

Two major contributions to the shift of the CO stretch vibrational frequency between free CO and chemisorbed CO/Cu(100) are identified. The overlap and consequent repulsion between the CO and metal orbitals leads to an increase in the frequency. The metal charge donation and dative bonding to CO 2π* leads to a decrease. © 1985.