“…Hence, the heavy metal ions increase the computation cost of high-level electronic structure theories. A way to reduce the computation is the Model Core Potential (MCP; Sakai et al, 1987;Miyoshi et al, 2005;Osanai et al, 2008ab;Mori et al, 2009), where the proper nodal structures of valence shell orbitals can be maintained by the projection operator technique. In the MCP scheme, only valence electrons are considered, and core electrons are replaced with 1-electron relativistic pseudo-potentials to decrease computational costs.…”