Embedding Wave Function Theory in Density Functional Theory

摘要

Because ab initio wave function theory (WFT) proceeds by making systematic approximations to the Schrodinger equation, it reliably makes predictions of the physical and chemical properties of atoms and molecules. By systematically relaxing these approximations (i.e. increasing the level of correlation or the size of the computational basis), one can obtain arbitrarily accurate solutions of the Schrodinger equation. Unfortunately, this accuracy and reliability require such exorbitant computational effort that high-level calculations can be applied only to relatively small systems. Density functional theory (DFT) is an attractive reformulation of quantum mechanics since it provides usually reasonable results at a fraction of the cost of traditional wave funtion methods. But as we do not know the exact exchange-correlation functional, we must resort to approximate functionals which may or may not prove reliable in any given system. And if these functionals give poor results, it is usually not possible to systematically improve the quality of the calculation within the DFT framework.