Algorithms for calculating the leading quantum electrodynamics P(1/r ³) correction with all-electron molecular explicitly correlated Gaussians

Algorithms for calculating the quantum electrodynamics Araki-Sucher correction for n-electron explicitly correlated molecular Gaussian functions with shifted centers are derived and implemented. The algorithms are tested in calculations concerning the H₂ molecule and applied in ground-state calculations of LiH and molecules. The implementation will significantly increase the accuracy of the calculations of potential energy surfaces of small diatomic and triatomic molecules and their rovibrational spectra.