Correlation consistent basis sets for actinides. II. The atoms Ac and Np-Lr

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Relativistic Quantum Chemistry

Background:

• Accurate theoretical calculations for heavy elements, particularly actinides, are challenging due to relativistic effects.
• Existing basis sets may not sufficiently capture electron correlations for these elements.
• Development of robust basis sets is crucial for reliable predictions in actinide chemistry.

Purpose of the Study:

• To report new correlation consistent basis sets optimized for actinide elements (Ac-Lr).
• To validate the effectiveness of these basis sets through atomic and molecular benchmark calculations.
• To provide accurate theoretical data for ionization potentials and atomization energies of actinides.

Main Methods:

• Optimization of basis sets using the all-electron third-order Douglas-Kroll-Hess (DKH3) scalar relativistic Hamiltonian.
• Development of valence and outer-core correlation sets (cc-pVnZ-DK3/cc-pVnZ-X2C and cc-pwCVnZ-DK3/cc-pwCVnZ-X2C).
• Calculations of atomic ionization potentials using the Feller-Peterson-Dixon (FPD) composite approach with multireference configuration interaction (MRCI).
• Calculation of molecular properties (IP and atomization energy of PuO2) using FPD and coupled cluster methods with spin-orbit coupling.

Main Results:

• New basis sets demonstrate excellent convergence towards complete basis set (CBS) limits for actinide ionization potentials.
• Calculated atomic ionization potentials show good agreement with experimental data when spin-orbit effects are included.
• For PuO2, the calculated ionization potential (159.8 kcal/mol) and atomization energy (305.6 kcal/mol) closely match experimental values.

Conclusions:

• The newly developed correlation consistent basis sets are effective for accurate relativistic calculations of actinide properties.
• These basis sets enable high-quality theoretical predictions for challenging actinide systems.
• The study provides reliable computational benchmarks for future research in actinide chemistry and physics.