First-Principles Calculations of the Structure and Energetics of Al/Water Interfaces of Relevance to Corrosion and Fatigue (funded by NASA)
The work seeks to apply first-principles simulation methods for determining the fundamental constants responsible for the deterioration of metal (specifically Al and Al alloys) properties in the presence of oxidizing conditions. These constants shall be expressed in terms of the affinity of Al for oxidizing species such as water, oxygen and hydroxide, and in the development of a metal-metal interaction potential to describe the perturbations induced as a result of this affinity. The proposed work therefore represents a natural merging of the work performed previously by the principal investigators, namely the atomistic calculations of water and hydrogen over transition metal surfaces, and the derivation of parameters for aluminum oxidation via first-principles means. Calculations for aluminum surfaces can be performed in a similar way as for transition metal surfaces, and will in fact avoid some of the difficulties of transition metal modeling, for example, convergence problems due to magnetization.
The work shall be divided up into three stages, according to year. An outline indicating the scheduled programs and the projected outcomes is given as a flowchart below. In the first year we shall consider the reactivity of water on the Al or Al alloy surface. This is essential to understanding the commencement of surface oxidation, synchronous with the deleterious process of hydrogen embrittlement, as water acts as both an oxidizing agent, and a source of hydrogen. In the second year we shall consider the effect of oxygen. Molecular oxygen is another oxidizing agent highly prevalent under normal conditions. In this second year we shall also consider various models for the development of a metal/metal interaction potential that takes into account the effects of the H2O and O2 environment. Finally, in the third year, we shall consider the synergism between H2O and O2 surface damage on the Al or Al alloy, and the perturbations required to account for this synergism with respect to the metal/metal potential. Additionally, H uptake effects will be further explored. Also, in this year, we will work with NASA and associates to develop a suite of multiscale modeling tools that can incorporate the first-principles parameters into a molecular dynamics /