Introduction

The CDM combines the computational, synthesis and characterization tools of modern chemistry to design, grow and test novel multifunctional solids for specific technological applications. We focus on one particular sub-class of multifunctional solids; those that combine phenomena enabled by polarity with additional functionalities that are currently considered incompatible, or even contraindicated. Polar solids exhibit an exceptionally wide range of properties that have enabled advanced technologies, such as high dielectric storage capacitors, piezoelectric microactuators, electro-optic devices, and ferroelectric memories. The building block of an extended polar solid is the coordination polyhedron, therefore we need to measure, understand and control the local chemical bonding that dictates the geometry of the coordination polyhedron leading to polarity. Important considerations include the geometry of the polyhedron (octahedron, tetrahedron, trigonal bipyramid, etc.) and distortions, such as cation off-centering displacements, that create or enhance the polarity of the polyhedron (Fig. (a) and (b)). The properties of the solid are also determined by the manner in which the polyhedra assemble in the crystal lattice of the functional material (Fig. (c) and (d)). So our challenge is three-fold: First to choose systems where the building blocks are polar, second to explore how to coerce these polar units to assemble with their dipoles adding constructively, and third, to create additional functionality in these polar materials.

(a) A non-polar coordination polyhedron (octahedron). (b) A polar coordination polyhedron. (c) Cooperative addition of polar behavior. (d) Cooperative canceling of polar behavior. Ferroelectric PbTiO3 and antiferroelectric PbZrO3 correspond respectively to schemes (c) and (d)[]. Large spheres are cations and small spheres are anions.

We are pursuing research in 5 related thematic areas: Theme I. Superferroelectrics & non-linear optical (NLO) materials; Theme II. Anion control of polar behavior. Theme III. Low loss microwave dielectrics with simultaneously high magnetic permeability; Theme IV. Ferromagnetic insulators and magnetic ferroelectrics (multiferroics) and Theme V. Layer-by-layer growth of multifunctional materials, and epitaxial deposition of metastable materials. In addition, we are pursuing one start-to-finish ``proof of concept'' multifunctional design problem (Theme VI) which is building on the tools and expertize that we develop during the course of the other projects.