Determination of vibrational energy relaxation rates of C-H,D,T stretching modes on hydrogen, deuterium, and tritium-terminated H,D,T/C(111) and H,D,T/C(110) diamond surfaces using molecular dynamics simulation: Thermal effect

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 stretches on a H/C(111) surface, the lifetimes at high temperatures are shortened much further not only by the rise in the temperature but also due to the thermal broadening of the resonance peaks in the force power spectra. The characteristics of power spectra and the resulting relaxation rates were analyzed using a simple model of a constrained diatomic bond in a harmonic bending potential field. The present results suggest that, since the resonance frequencies of C-H stretches are located within the border region between the 1:2 and 1:3 resonance domains, the vibrational energy relaxation of C-H stretches may differ by more than an order of one on different monohydrided low index unreconstructed diamond surfaces in contrast to the lifetimes of C-D,T stretches on these diamond surfaces, which are all on the same time scale at a given temperature.