Numerical Simulation Of Interaction Between Atomic Oxygen And Zirconium

The interaction between atomic oxygen and zirconium was numericallysimulated using a ReaxFF-force-field based molecular dynamics method. Thesimulated calculation was conducted on a model with1000atomic oxygensinteracted with Zr（001） and/or Zr（100）. The simulation characterized the surfaceoxide produced by interaction between atomic oxygen and zirconium, such as thethickness, structure, growth mechanism, stability and zirconium valence of the oxide,which is verified by atomic oxygen exposure test.The results showed that, the most stable adsorption site of atomic oxygen inZr（001） and/or Zr（100） is octahedral interstice and hollow site. The oxide layerproduced by atomic oxygen and zirconium is consisted of outer layer and inner layer.The maximum thickness of the oxide layer is approximately2.0nm under the atomicoxygen with5eV kinetic energy, and about0.9nm under thermal atomic oxygen. Thetemperature has little effect on the oxide thickness within the range of300K-500K.The growth of oxide is through oxygen atom diffusing into Zr substrate andzirconium atom diffusing toward outer sureface.The oxide layer prevets the subsequent thermal atomic oxygen entering intozirconium substrate when it becomes stable under interaction between thermalatomic oxygen and zirconium. In contrast with thermal atomic oxygen, the atomicoxygen with5eV can overcome the energy barrier and enter into oxide. It indicatesthat the5eV atomic is capable of react with zirconium. Therefore the stability ofoxide is lower under interaction of5eV atomic oxygen than that of thermal oxygen,which is in accordance with the TEM and AFM analysis on the zirconic surfaceexposed under atomic oxygen.The interaction between thermal and/or5eV atomic oxygen and Zr results information of amorphous oxide. The zirconic valence has an outside-in transition ofZr⁴⁺â†'Zr³⁺â†'Zr²⁺â†'Zr¹⁺in oxide, which is consistent with the XPS analyses afterztomic oxygen exposure...