Parallelization of Two-Electron Integrals in Spin-Free Infinite-Order Two-Component Hamiltonian

A parallelization scheme for computing two-electron integrals in a two-component relativistic theory was developed based on the spin-free infinite-order two-component Hamiltonian. The proposed algorithm utilizes a distributed data interface and distributed memory in the GAMESS program. Its efficiency was demonstrated by numerical assessments. Furthermore, the proposed parallelization algorithm was implemented by combining it with a local unitary transformation, which is a linear-scaling technique for a two-component relativistic Hamiltonian. The multiprocess calculation of the total energy of the metal complex [Pt₁₃(C₇H₇)₆]²⁺ indicates the usefulness of the parallel program developed in this study.