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Molecular dynamics simulations were carried out to determine the vibrational energy relaxation rates for C–H,D,T stretches on hydrogen-, deuterium-, and tritium-terminated H,D,T/C(111) and H,D,T/C(110) diamond surfaces at high temperatures based on the Bloch–Redfield theory and the calculated power spectra of fluctuating force along C–H,D,T stretches. The lifetime of C–H stretches on H/(110) surfaces at room temperature was found to be 0.8 ps, which is much shorter than the calculated lifetime of 30 ps on a H/C(111) surface attributed to 1:3 resonance. This is due to the blueshift of the 1:2 resonance domain in the force power spectra for a H/C(110) surface. The lifetimes of C–H stretches on a H/C(110) surface and C–D,T stretches on both D,T/C(111) and D,T/C(110) surfaces, which all undergo 1:2 resonance energy relaxation, are all on the time scale of tenths of a picosecond at room temperature and are approximately inversely proportional to the square of the temperature at high temperatures. For C–H stret...

The vibrational energy relaxation rate of an excited C–H stretching mode on the hydrogen‐terminated H/C(111)1×1 surface is calculated using Bloch–Redfield theory combined with classical molecular dynamics. The lifetime of an excited state is determined by the strength of the power spectrum of the force on the stretching mode at the resonance frequency. The lifetime of the first excited state is found to be 60 ps at 300 K which is shorter than the Si–H stretching mode lifetime on the H/Si(111)1×1 surface. The lifetime of the v=2 first overtone state is found to be 200 times shorter (0.30 ps). Analysis of the power spectrum of the fluctuating force along the C–H bond suggests that the mechanism of the energy relaxation for the v=1 stretching state on the H/C(111)1×1 surface is due to lower‐order interactions than on the H/Si(111)1×1 surface. The predicted fast relaxation of the overtone state may cast some doubt on the observability of that state.

Path integral quantum transition state theory is implemented to calculate the diffusion constant for atomic hydrogen on metal surfaces at low coverage. The path integral theory provides a unified computational methodology to study the influence on the diffusion constant from multidimensional tunneling, vibrational mode quantization, surface distortion, and phonon thermal fluctuations. An approximate technique has also been employed to incorporate the dissipative effect from the electron–hole pair excitations of the metal. The hydrogen diffusion rates on two model metal surfaces are calculated. These surface models are (1) a simple rigid model of the Cu(100) surface allowing a comparison with previous theoretical results, and (2) a more realistic moving model of the Cu(100) surface to examine the effects of surface atom motion. The quantum diffusion constant for hydrogen is calculated over a temperature range of 100–300 K. The largest effect from the moving lattice atoms is found to be the surface distortion effect, leading to a 5% modification of the activation free energy for site‐to‐site hopping. The phonon thermal fluctuations are not found to significantly enhance or dissipate the tunneling at low temperatures. The electron–hole pair dissipation is, however, estimated to have an effect on the tunneling behavior at the lowest temperature studied (100 K).