DFT + U as a reliable method for efficient ab initio calculations of nuclear materials

• Benchmarking of the parameter free DFT + ULR method for f-elements molecules and solids is performed.
• DFT + ULR method gives equally good results for U, Np, Pu and Am molecular compounds.
• The structures and formation enthalpies of xenotime ceramics are reproduced by calculations.

Density functional theory (DFT)-based ab initio methods become standard research tools in various research fields, including nuclear materials science. However, having strongly correlated f-electrons, lanthanide- and actinide-bearing nuclear materials are computationally challenging for DFT methods and straightforward DFT calculations of these materials can easily produce false results. In this contribution we benchmark the DFT + U method, with the Hubbard U parameter derived ab initio, for prediction of structural and thermochemical parameters of nuclear materials, including various actinide-bearing molecular complexes and lanthanide-bearing monazite- and xenotime-type prospective ceramic nuclear waste host forms. Our studies show that the applied DFT + U method improves significantly prediction of DFT by producing results with uncertainties similar to those of the higher order, but computationally unfeasible ab initio methods, and the experimental data, and thus allows for reliable and feasible ab initio computation of even chemically complex nuclear materials.