A new generation of effective core potentials: selected Lanthanides and heavy elements

TL;DR

This paper develops new correlation-consistent effective core potentials for selected heavy atoms and f-elements, improving accuracy and transferability for materials and chemical simulations.

Contribution

It introduces a novel construction of ccECPs for heavy and f-elements using relativistic coupled-cluster methods and optimized transferability, addressing challenges with f-element cores.

Findings

Achieved high accuracy in modeling heavy atoms and f-elements.

Constructed ccECPs suitable for plane wave calculations.

Demonstrated improved transferability across molecules.

Abstract

We construct correlation-consistent effective core potentials (ccECPs) for a selected set of heavy atoms and f-elements that are of significant current interest in materials and chemical applications, including Y, Zr, Nb, Rh, Ta, Re, Pt, Gd, and Tb. As customary, ccECPs consist of spin-orbit averaged relativistic effective potential (AREP) and effective spin-orbit (SO) terms. For the AREP part, our constructions are carried out within a relativistic coupled-cluster framework while also taking into objective function one-particle characteristics for improved convergence in optimizations. The transferability is adjusted using binding curves of hydride and oxide molecules. We address the difficulties encountered with f-elements, such as the presence of large cores and multiple near-degeneracies of excited levels. For these elements, we construct ccECPs with core-valence partitioning that includes 4f-subshell in the valence space. The developed ccECPs achieve an excellent balance between accuracy, size of the valence space, and transferability and are also suitable to be used in plane wave codes with reasonable energy cutoffs.