ZORA double zeta basis sets for fifth row elements: Application in studies of electronic structures of atoms and molecules

[Display omitted] •Accurate all-electron basis sets for fifth-row atoms are constructed.•Ionization energies and polarizabilities of some elements were calculated.•Electronic structures of ten diatomic molecules were studied.•The performances of the ZORA and DKH Hamiltonians are assessed. Segmented all-electron basis set of double zeta valence quality plus polarization functions (DZP) to be used with the zero-order regular approximation (ZORA) scalar relativistic Hamiltonian was developed for the elements Cs, Ba, La, and from Hf to Rn. This set was augmented with diffuse functions for the purpose of describing electrons distant from atomic nuclei. Using the ZORA-B3LYP method, some atomic and molecular properties are computed. Benchmark theoretical results and experimental data were used to evaluate the performance of the DZP-ZORA and ADZP-ZORA basis sets. Despite their small sizes, these sets have proven to be accurate and reliable and can also be used in property calculations involving electrons not only from the outer shells, but also from the inner shells. Comparison of second order Douglas-Kroll-Hess and ZORA results was made.