[SY-A2] Two-component Dirac-Kohn-Sham calculation for multiscale modeling of materials
It is known well that some specific properties and characteristics of materials cannot be exactly simulated without considering the relativistic effect, whereas general first-principles electronic-state calculation technique for material systems has been established on the basis of the Schrödinger equation under non-relativistic limit. The most fundamental idea to treat the relativistic effect is the electronic-state calculation based on the Dirac equation from the viewpoint of the relativistic quantum mechanics, and the effective methodologies, such as multiconfiguration Dirac-Fock and Dirac-Kohn-Sham (DKS) methods, have been developed for leading to exact electronic states. The relativistic calculation based on the Dirac equation originally uses 4-component spinors, which consist of 2 large components and 2 small components. However, the calculation with 4-component spinors is computationally too expensive to perform for material systems practically. To avoid the calculation with 4-component spinors, some theoretical treatments of calculation with 2-component spinors, such as zeroth-order regular approximation (ZORA), infinite-order regular approximation (IORA), relativistic scheme by elimination of small components (RESC), and high-order Douglas-Kroll transformation, have been developed in the field of molecular physics and chemistry. For the application of these methods to material systems under the periodic boundary condition, some special techniques should be required to adopt the elimination of small components to the basis set by plane wave or projector augmented wave. In this study, examples of the DKS calculation with 2-component spinors by ZORA, IORA, and RESC methods shall be presented for some typical material systems. The details of techniques how to eliminate small components of spinors and the differences in specific properties and characteristics of target materials according to relativistic methodologies will be discussed in the conference.