Theoretical studies of hydrogen dynamics on surfaces: Diffusion and vibrational relaxation. Ph.D. Thesis
The theme of the thesis contained herein comprises two subjects of hydrogen dynamics on surfaces, which are hydrogen diffusion on metal surfaces and vibrational relaxation dynamics on semiconductor surfaces. In the study of hydrogen diffusion, a path integral quantum transition state theory is implemented to calculate the diffusion constant for atomic hydrogen on metal surfaces at low coverage. 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. In the research of the vibrational relaxation dynamics on semiconductor surface, the vibrational energy relaxation rate of an excited C-H stretching mode on the hydrogen-terminated H/C(111)1 x 1 surface is calculated using Bloch-Redfield theory combined with classical molecular dynamics. The lifetime of the first excited state is found to be 60 ps at 300K. Analysis of the power spectrum of the fluctuating force along the C-R bond suggests that the mechanism of the energy relaxation for the v = 1 stretching state on the H/C(111)1 x 1 surface is due to lower-order interactions than on the H/Si(111)1 x 1 surface. The vibrational energy relaxation rates of the excited Si-H stretching modes on the stepped monohydride H-terminated H/Si(111)1 x 1 surface were calculated as well. The structure of the surface and vibrational frequencies on the surface were investigated using the Car-Parrinello molecular dynamics method.
- Research Organization:
- Pennsylvania Univ., Philadelphia, PA (United States)
- OSTI ID:
- 147182
- Resource Relation:
- Other Information: TH: Ph.D. Thesis; PBD: 1994
- Country of Publication:
- United States
- Language:
- English
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