PhD project: Making and using an interatomic forcefield for titanium alloys

Project description

Molecular dynamics simulation relies entirely on the model describing   forces acting between atoms.  Sensible models exist for metallic and oxide systems, but at present there are no simple ways to combine them.  In this project you will devise methods to describe interactions in and between titanium and titanium dioxide.

Titanium alloys have widespread industrial usage, and are relatively immune to oxidation thanks to the formation of a thin oxide layer which blocks diffusion of further oxygen atoms into the bulk. Surprisingly, this layer is not thermodynamically stable, but it persists for many years.   At high temperature, Ti oxidises very rapidly, so Ti alloys cannot be used for applications such as turbine blades.  At very high temperature, Ti oxidises so fast that it burns. There is some evidence that certain alloying additions, such as Nb and V, can eliminate this effect.  Nobody knows why.  Until recently it was believed that these 5-valent ions stopped oxygen from migrating through the oxide layer, until our calculations in Mamina showed that Nb and V are insoluble in the oxide - a prediction which was then proven experimentally.  

A new method for developing interatomic forces comes from linking the forces generated by accurate DFT calculations to a machine-learning process which fits the potential model parameters. This model can then be applied to million-atom molecular dynamics systems to directly simulate processes at the atomic scale. With the potential model, you will simulate the oxidation process, which will lead to an understanding of how oxidation proceeds, and how it can be blocked.

The project follows on from an EU training programme based around designing Ti alloys, MAMINA .  We have good contacts with laboratories in Braunschweig, and if you wish to conduct experiments in support of the calculations, this will be a possibility.

Oxidation resistance by DFT

Interatomic model for Titanium

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