A CLASSICAL MOLECULAR-DYNAMICS STUDY OF THE VIBRATIONAL DYNAMICS OF THE H C(111)-(1X1) SYSTEM/

Vibrational dynamics of H atoms on C(111) surface was studied by class ical molecular dynamics method with the use of a harmonic force field for the diamond lattice and of both harmonic and anharmonic potential for the C-H bond. Results of the calculations show a strong coupling o f the C-C-H bending vibration to the the lattice modes. In addition to the experimentally observed band of the bending vibration at 1331 cm( -1) the calculations predict a band at ca. 1000 cm(-1) in the infrared spectrum of the system with the surface-parallel polarization. :Resul ts of the study show a strong dynamic anharmonicity of the large ampli tude vibrations of hydrogen atoms. Simulations of the C-H stretching e nergy relaxation lead to values of the energy relaxation time close to those measured. The agreement is improved in the anharmonic model for the C-H bond potential. Results of the calculations point to the inte raction between the C-H stretching vibration and the overtone of the C -C-H bending vibration as the main channel for the energy relaxation. (C) 1998 Elsevier Science B.V.