Molecular-dynamics study of the C-H vibrational spectra on diamond (111) and (100) surfaces

The vibrational properties of the C-H stretch and bend modes on diamond C(100) and C(111) have been calculated by Fourier transform of the autocorrelation functions of the velocities obtained by first-principles molecular-dynamics simulations. We find that the increase of the temperature slightly softens both stretch and bend modes and the replacement of H by D reduces the stretching frequency by a factor of 0.74. By comparison between the vibrational frequencies of the C-H bonds on C(111) and C(100) and in the CH4 and C2H6 molecules, we find that the C-H bend mode is softened on both C(111) and C(100), while the stretch mode is hardened slightly on C(100). [S0163-1829(99)16947-9].