Quantum-mechanical investigation of bonding and vibrational properties of CO-adsorbed copper

Density functional theory calculations are performed to determine the nature of vibrational modes associated with carbon monoxide chemisorbed to the copper (100) surface. The electronic states and charge density are determined using a plane-wave pseudopotential method within the local density approximation. The surface is modeled using a periodic slab geometry, and the force constant matrix is computed from first principles by displacing each atom in turn and determining the resulting forces on it and all other atoms. This matrix is then diagona]ized to yield normal-mode polarization vectors and frequencies. The eigenvectors provide information about the strength of coupling between copper atom motions and CO vibrations. The computed vibrational spectrum is used to predict the transient response of the system to nonequilibrium heating, and the results are compared with recent pulse-laser experiments on this system.5'6