Material science

Materials science, if defined in terms of length scales, spans the five decades from nanometers to hundreds of micrometers. While traditional materials engineering deals with continuum models on the large scale, the effective properties are determined by features on the small scale such as dislocations, grains, precipitations, and even molecules and atoms. Thus, materials design is about manipulating small scale phenomena by proper processing e.g., chemical and thermal,
to obtain favorable large-scale properties. Quantum-mechanical simulations play an important role in materials science at the nano-end of the length scale, for instance in order to understand
dislocations, magnetism, crystal structure, surface structure, and catalytic behavior.

Sample projects

Simulation of iron structure in the Earth's core
The Earth's core consists mainly of iron and is a sphere with a radius of about 3500 km. The outer part of the core is liquid and the inner
part is solid. Properties of iron at the inner core conditions are of ultimate importance for understanding how the Earth functions. These properties, in turn, critically depend on the atomic structure of the iron phase which is stable at these conditions. In a recent paper large
scale calculations performed by a group at the department of Materials Science and Engineering predict that the stable iron has bcc structure, i.e. the atoms of iron are positioned in the corners of cube surrounding the atom in the cube's center. This is an unexpected result, since it has
been believed for about 40 years that iron in the inner core is stable in the hexagonal close packed structure. The amount of thermal energy and temperature, at which the iron inner core remains solid, critically depends on the structure of the iron phase.

Simulation of structural and phase changes
The simulation of microstructure formation in materials is studied in a collaboration between the department of Materials Science and Engineering and the department of Mechanics. A common microstructural process in solidification is the growth of a dendritic crystal in an undercooled melt, as shown in the figure. The complicated shape develops due to inherent instabilities in the evolution of the phase boundary, and is infuenced by the anisotropy of the forming crystalline phase. The simulation was done by the phase field method, which treats the interface as a smooth but steep transition.