Solving the Dirac Equation with Nonlocal Potential by Imaginary Time Step Method

The imaginary time step (ITS) method is applied to solve the Dirac equation with the nonlocal potential in coordinate space by the ITS evolution for the corresponding Schrödinger-like equation for the upper component. It is demonstrated that the ITS evolution can be equivalently performed for the Schrödinger-like equation with or without localization. The latter algorithm is recommended in the application for the reason of simplicity and efficiency. The feasibility and reliability of this algorithm are also illustrated by taking the nucleus ¹⁶O as an example, where the same results as the shooting method for the Dirac equation with localized effective potentials are obtained.