Considering Density Functional Approaches for Actinide Species: The An66 Molecule Set

Area of Science:

• Computational chemistry
• Quantum chemistry
• Actinide chemistry

Background:

• Accurate prediction of actinide compound properties is essential for various applications.
• Density Functional Theory (DFT) is a common method, but its accuracy for heavy elements like actinides can be limited.
• Spin-orbit (SO) coupling is a relativistic effect that can significantly influence electronic structure and energetics.

Purpose of the Study:

• To systematically evaluate the importance of spin-orbit effects in predicting the energetic properties of actinide compounds.
• To compare the performance of 18 different density functionals, with and without spin-orbit coupling, for actinide systems.
• To investigate the influence of basis set choice and relativistic treatments on the calculated enthalpies of formation.

Main Methods:

• Calculated enthalpies of formation for 66 actinide compounds (An66 set) using 18 density functionals.
• Compared spin-orbit (SO) DFT calculations with non-spin-orbit (non-SO) DFT calculations.
• Investigated the effect of basis sets, including Stuttgart ANO basis sets with relativistic effective core potentials (RECP) and all-electron Douglas-Kroll-Hess methods.

Main Results:

• Spin-orbit coupling was found to be crucial for accurately predicting the energetic properties of actinide compounds.
• The inclusion of spin-orbit effects led to improved agreement with experimental enthalpies of formation for many compounds.
• Different density functionals showed varying performance, highlighting the need for careful selection when studying actinide systems.

Conclusions:

• Spin-orbit effects are indispensable for reliable theoretical predictions of actinide compound energetics.
• The choice of density functional and relativistic treatment significantly impacts the accuracy of calculated properties.
• This work provides valuable guidance for computational chemists studying actinide compounds.