When a solid changes its internal structure, interesting new physical properties may appear. Often these properties can be predicted and the material can be utilized for a particular purpose, for example, as superconductors, as ferroelectrics in copiers, as piezoelectrics in sensors, etc. We apply principles of group theory to the study these transitions between different crystalline structures. This project has been ongoing since 1983. We have developed software that allows us to generalize our group-theoretical methods to a large number of possible cases that may be observed experimentally.
Crystal defects have a profound effect on macroscopic properties of materials.
These include mechanical properties, such as hardness, strength, and elasticity, and electrical, magnetic, and electronic properties, such as ionic conductivity, semiconductor and device behavior, and internal magnetic fields. Physicists are now beginning to design materials with desired properties, often building layered materials for this purpose. The details of these materials and interactions on an atomic scale are important for producing the properties which are sought. In addition, the size of a cluster of atoms, the symmetries and bonding on surfaces and at interfaces, strongly affect electronic and magnetic properties of materials. We are now focusing more of our attention on nanoclusters of a few atoms, which promise to be the basis for electronic devices of the future.