Development of embedding density functional theory for efficient electronic structure calculations

Abstract

Kohn-Sham density functional theory (KS-DFT) is widely used among the not only physical chemists, but also the organic and inorganic chemists. Its accuracy and efficiency depends on the various numerical techniques, including the choice of the basis set, pseudopotential or the projector augmented wave method, and other techniques removing the numerical artifact often arises from the incomplete basis set. Apart from those numerical techniques, the choice of exchange-correlation functional is crucial factor deciding both the accuracy and efficiency. Conventionally used exchange-correlation functionals often shows incorrect asymptotic behavior and discrepancy from the theory. Sometimes they include an integral having no analytic form, thus computationally cumbersome. In this dissertation, development of ACE-Molecule, a real-space quantum chemistry package and their numerical techniques and properties of real-space basis will be presented. Next, an efficient and accurate calculation of excited states using simple range-separated localized exact-exchange hybrid will be presented. Another choice to achieve the high accuracy and efficiency of quantum chemistry calculation is to combine two theories together. In the last part of this dissertation, partitioning of orbital space and embedding two different theories in the orbital space will be presented for efficient calculations. The present embedding scheme aims to construct the embedding region using theoretically well-defined partitioning, and to not require numerical optimization of the embedding potential. This scheme shows stable convergence and accurately describe spin state of metal complex, and efficiently reduces the computational time compared to the global hybrid scheme.