Conceptual density functional theory role

Fukui, K. 1987. Role of frontier orbitals in chemical reactions. Science 218 747-754. Geerlings, P., De Proft, F., and W. Langenaeker. 2003. Conceptual density functional theory. Chem. Rev. 103 1793-1873. 

Conceptual density functional theory has been quite successful in providing quantitative definitions for popular qualitative chemical concepts like electronegativity , hardness and electrophilicity . It has also been found to be useful in providing firm theoretical bases for the associated electronic structure principles. Various global and local reactivity descriptors " have played an important role in analyzing bonding, reactivity, stability, interactions and aromaticity in a variety of many-electron systems as well as a host of their physico-chemical properties. 

The role of quantum theory in chemistry has a history of almost 100 years, and the advances have been important. Nowadays, it is possible to do quantitative predictions with chemical accuracy for middle-size molecules, and some type of calculations, especially density functional-based methodologies, are routinely done in many chemical laboratories. One very important aspect on the influence of quantum theory in chemistry is the one of understanding. There are many chemical concepts which can be understood only through the laws of quantum mechanics. This chapter is about conceptual understanding and is not about the other very important issue of computing with chemical accuracy. 

Compared with density functional methods, Hartree-Fock-based approaches play a less important role in electronic structure calculations of solids and surfaces, although the exact treatment of the exchange terms is conceptually very appealing. The inclusion of electronic correlation effects in the form of perturbation theory, coupled cluster methods, or configuration interaction expansion is very well developed for the calculation of molecular properties. However, in most cases these approaches are not suited for solid state systems. 

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