A new generation of effective core potentials from spin-orbit and correlated calculations: selected heavy elements

Recently, we have developed a new generation of correlation consistent effective core potentials (ccECP) for elements H-Kr. Here we expand to heavier elements, in particular, to a selected set of I, Bi, Pd, W, Ag, and Au. The chosen set is used to optimize the procedure for atoms with significant spin-orbit effects. First, we generate averaged relativistic effective potentials (AREP) that correspond to commonly used semi-local form. This AREP part follows the established techniques such as weighted atomic iso-spectrality with all-electron excitations and norm-conservation. Second, effective spin-orbit terms are generated using energy-consistency for pertinent states such as multiplet splitting and/or low-lying states using 2-component spinor formalism within a chosen CI active space. The quality of resulting spin-orbit ccECPs is assessed by carrying out fixed-phase diffusion Monte Carlo (DMC) calculations for the mentioned atomic states and comparing them with experimental values. Transferability is further tested by calculations of binding energies for the corresponding dimers using DMC and cross-checking with the experimental result.