Gaussian basis sets of quadruple zeta quality for potassium through xenon: application in CCSD(T) atomic and molecular property calculations

All-electron segmented contracted quadruple zeta valence plus polarization function (QZP) basis sets for the elements from K to Xe were constructed to be used in conjunction with the non-relativistic and Douglas–Kroll–Hess (DKH) Hamiltonians. The QZP-DKH set is obtained from the original QZP basis set, that is, the values of the contraction coefficients were re-optimized using the relativistic DKH Hamiltonian. This extends earlier works on segmented contracted QZ basis set for atoms H–Ar. At the coupled-cluster level of theory, the convergence of atomic ionization energy as well as of molecular spectroscopic constants as a function of basis set size is examined. Additional improvements on spectroscopic constants were achieved by applying corrections due to core–valence correlation and spin–orbit effects. This leads to estimates for the spectroscopic constants of various diatomics in gaseous phase. One verifies that the experimental and benchmark theoretical bond lengths, atomization energies, and harmonic vibrational frequencies can be reproduced well with the QZP-DKH set.