120th General Meeting of the KCS

Type Symposium
Area Recent Progress in Electronic Structure Theory
Room No. Room 208+209+210
Time THU 15:10-:
Code PHYS1-5
Subject A local exact exchange potential method for accurate excited state calculations
Authors WOO YOUN KIM
Department of Chemistry, Korea Advanced Institute of Science and Technology, Korea
Abstract Density functional theory (DFT) has been an essential tool for electronic structure calculations in various fields. In particular, its hybrid method including the Hartree–Fock (HF) exchange term remarkably enhanced the reliability of DFT for chemical applications and computational material design. However, accuracy for excited state calculations is yet to be improved. A trial with another new density functional may not be desired, as is evident from previous attempts. Instead, we tried to find a way to improve the accuracy of existing functionals. There are two different types of exchange–correlation potentials that can be derived from hybrid functionals. In conventional approaches, the HF exchange operator is adopted as a part of Kohn-Sham (KS) potential. On the other hand, the optimized effective potential (OEP) method provides another way to incorporate the exact exchange in a mean field picture by constructing a local potential from the non-local HF exchange energy. Thus, one may construct a local version of HF that is equivalent to the exchange-only OEP KS-DFT. It has been known that the exchange-only OEP KS theory gives similar occupied orbitals to HF, while its virtual orbitals are different from those of HF. Since KS virtual orbitals are closer to optical excitations, we expect that the OEP exact exchange would be more suitable to describing excited states than that of HF. Here, we show that such a local multiplicative potential can be derived from existing hybrid functionals using the OEP method. We investigate its performance for molecular excited states. Furthermore, we find that the new approach enormously accelerates computational speed of grid-based methods compared to the conventional one, which is desirable for large-scale calculations.
E-mail wooyoun@kaist.ac.kr