Quantum theory of atoms in molecules and the AIMAll software Chapter 3

Chemical bonding in the twenty-first century is inexorably linked to the application of quantum mechanics to chemistry. Today, the electronic structure of systems of moderate complexity can be reliably obtained even with desktop computers. The latter spit out intricate wavefunctions that need be analyzed if chemical insight, not only energies or energy differences, are needed. However, the large dimensionality of ? poses a severe problem to the rationalization of chemical phenomena. As already noticed by Van Vleck [1], the amount of information stored in a wavefunction when the number of electrons of a system exceeds N ? 1000 is so large that it escapes human comprehension, so that an information compression technique is needed.