Toward structure-function relations - A hybrid quantum/classical approach

The calculation of electronic structure of materials by first principles quantum methods is now essentially routine, thanks to development of Density Functional approaches. However, the electronic structure depends in detail upon the nuclear positions, which are not generally known in advance. The prediction and verification of atomic positions- the geometrical configuration- of a complex molecule like a protein, or of a chemically reactive surface, or of a doped solid interface, for example, begins to yield to atomistic simulations based upon classical or semiclassical force-fields. A significant remaining problem is to couple together quantum and classical methodologies on several length- and time-scales which would be capable of carrying information forward into the continuum regime of materials modelling. We describe a particular approach to the so-called multiscale modelling problem spanning the range 1-1000 _and 1-10⁷ femtosec and its intended applications to predicting structure-function relationships required for materials analysis and design. Principles are illustrated by three examples: an isolated protein, a defective oxide surface, and a bioceramic analog.