Ni <sub> 3 </ Sub> Al Surface H And O Atoms Adsorbed First Principles

The dissertation is devoted to the study of the adsorption hydrogen and oxygen on Ni3Al surfaces, as well as boron doped effect on the adsorption of hydrogen on Ni3Al (111) surface from first principles. Our calculated results gain a better understanding of the microscopic mechanism of environment hydrogen brittlement and give a theoretical foundation for the further experiment.At the first part of this paper, the basic principles of crystal are introduced, and follow this is a summary of former investigation of environment hydrogen brittlement by experiment. In the second chapter, the density function theory is presented briefly. And the next two chapters give our result of oxygen and hydrogen adsorption on Ni3Al surfaces.On one hand, the adsorption of hydrogen on the clean and B-doped Ni3Al (111) surface are studied. Our results show that hydrogen atoms are apt to be adsorbed on the surface hole sites when it is the case of single atom adsorption. However, in this case, B atom likes the octahedral site between the first and the second layer of the surface with Ni as all of it's nearest atoms. In low coverage case, the surface hexagon compact package (hcp) site with a Al atom lying in the second layer is most favorite for hydrogen. And when there is a doped boron atom at it's favorite site, the stable site for hydrogen atom doesn't change and hydrogen's favorite site becomes more stable. However, the less stable site is not so stable as before. Our calculated results show that both hydrogen and boron atoms are apt to adsorb in Ni rich environment. The doped boron atom has some affection on the adsorption of hydrogen.On the other hand, we have studied the oxygen adsorption on Ni3Al (111) and (100) surfaces. In this investigation, two surface modules are designed: (100) and (111) surfaces. The results show that oxygen atom likes aluminum atom better. Because of the content of aluminum of (100) surface is more than that of (111) surface, it's easier for oxygen to adsorbs on the (100) surface. And the sensitivity of surfaces for oxygen adsorption on Ni3Al surfaces is analyzed from theoretical side.