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Surface stoichiometry and the initial oxidation of NiAl(110)
A Y Lozovoi1, A Alavi, M W Finnis
1Atomistic Simulation Group, School of Mathematics and Physics, Queen's University, Belfast BT7 1NN, United Kingdom.
Physical Review Letters
|September 16, 2000
Summary
Selective oxidation of Nickel-Aluminum (NiAl) surfaces involves atomic rearrangement and point defects. Oxygen presence favors Ni vacancies, driving NiAl oxide stability through nickel expulsion.
Area of Science:
- Materials Science
- Surface Science
- Computational Chemistry
Background:
- Selective alloy oxidation involves atomic redistribution near surfaces.
- Point defects play a crucial role in surface processes like oxidation.
- Understanding NiAl oxidation is key for material stability and applications.
Purpose of the Study:
- To investigate the atomic mechanisms of selective oxidation on NiAl surfaces.
- To determine the role of point defects in the initial stages of NiAl oxidation.
- To elucidate the driving forces behind NiAl oxide layer stability.
Main Methods:
- Utilized ab initio density-functional theory (DFT) calculations.
- Analyzed defect formation and migration energies at the NiAl surface.
- Modeled initial oxidation scenarios for Ni-rich and Al-rich NiAl.
Main Results:
- Identified favorable creation of exchange defects near the NiAl surface with oxygen.
- Found significant segregation of Ni vacancies to the top layer in the presence of oxygen.
- Observed an additional energy barrier for oxidation on the Ni-rich side compared to the Al-rich side.
Conclusions:
- Oxygen-induced Ni vacancies and exchange defects are crucial for NiAl surface oxidation.
- The stability of NiAl oxide is driven by the expulsion of Ni atoms from the forming oxide layer.
- Oxidation pathways differ between Ni-rich and Al-rich NiAl surfaces.