All-Electron Scalar Relativistic Basis Sets for the Lanthanides.

Segmented all-electron relativistically contracted (SARC) basis sets are constructed for the elements 57La-71Lu and optimized for density functional theory (DFT) applications. The basis sets are intended for use in combination with the DKH2 or ZORA scalar relativistic Hamiltonians for which individually optimized contractions are provided. Significant computational advantages can be realized owing to the loose contraction of the SARC basis sets compared to generally contracted basis sets, while their compact size allows them to replace effective core potentials for routine studies of lanthanide complexes. The new basis sets are evaluated in DFT calculations of the first four ionization energies of the lanthanides. They yield results that accurately reproduce the experimental trends, confirming a balanced treatment of different electronic configurations. The performance of the basis sets is further assessed in molecular systems with a comprehensive study of the lanthanide trihalides. Despite their compact size, the SARC basis sets demonstrate consistent, efficient, and reliable performance and will be especially useful in calculations of molecular properties that require explicit treatment of the core electrons.