Quantum crystallography, a developing area of computational chemistry extending to macromolecules

We describe the concept of quantum crystallography (QCr) and present examples of its potential as a technique for facilitating computational chemistry, particularly, applications of quantum mechanics. Structural information has been used to facilitate quantum-mechanical calculations for several decades. Recent advances in theory and computational facilities have led to research opportunities that could be considered only in the past several years. We focus on the feasibility of applications of quantum mechanics to macromolecules. The approach used involves the concept of calculations based on fragments of molecules. The method for constructing fragments, their composition, and how they are assembled to form a projector matrix are discussed without the introduction of mathematical detail. Papers that provide the theoretical basis for QCr and our method for making fragment calculations are referenced, and some initial calculations are described here.