Deflation techniques in quantum chemistry: Excited states from ground states (Review)

摘要

Applications of deflation techniques to the study of excited states of quantum systems are analyzed. It is demonstrated how these methods allow us to transform the excited state problem of one Hamiltonian, into the ground state problem of an auxiliary one. As an example, potential application in the density functional treatment of excited states is discussed. The inclusion of approximations in this scheme, such as the solution of the proposed model within a finite basis set is discussed. An extension of the Hartree-Fock (HF) method to excited states is presented. This new treatment includes previous self consistent field extensions to excited states and provides us with a way to obtain the HF extension to excited states of any ground state method. These results make the excited states of a system accessible through all ground state theoretical techniques. ? 2013 Wiley Periodicals, Inc. Understanding the properties of the excited states of molecular systems is of paramount importance in different fields (e.g., design of photovoltaic devices). However, studying excited states is a challenge greater than studying ground states. This work shows how ground state theoretical techniques can be used to tackle excited state problems. This simplifies the study of excited states, opening a wide range of techniques to analyze them.