Hillert Materials Modeling Colloquium series XIV: ab initio thermodynamics for actinide systems

The early (or light) actinides Th-Pu have physical properties that are largely understood in terms of the bonding character of dominating 5f electrons. More generally for heavier actinides and compounds, the picture is more complex. In the presentation we will show some examples of actinide materials where the itinerant (bonding) 5f-electron description is appropriate. In addition to ground-state properties such as atomic volume, bulk modulus, and elastic constants, we attempt to model thermodynamics from parameter-free first-principles theory. By combining lattice-dynamics from the self-consistent-phonon method with accurate electronic structure, we determine Gibbs free energies and other thermodynamic properties. Some of these, such as heat capacity or thermal expansion, can be directly compared with experiments while for the Gibbs free energy we use CALPHAD results that are derived from thermodynamically consistent representations of available experimental data. Examples include uranium [1], U-6Nb [2,3], and plutonium [4].

This work was performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344.

Litterature

1. Söderlind, P. et al. High-temperature thermodynamics of uranium from ab initio modeling. Appl. Sci. 2023, 13, 2123.
2. Söderlind, P. et al. Mechanical and thermal properties of uranium and U-6Nb alloy from first-principles theory. Appl. Sci. 2021, 11, 5643.
3. Landa, A. et al. Phase stability in U-6Nb alloy doped with Ti from first principles theory. Appl. Sci. 2020, 10, 3417.
4. Söderlind, P., Landa, A., Sadigh, B. Density-functional theory for plutonium. Adv. Phys. 2019, 68, 1.

Lecturer

Per Söderlind received his PhD in 1994 at Uppsala University, Sweden, under the supervision of professor Börje Johansson. He was postdoc at Lawrence Livermore National Laboratory between 1994 and 1996. Since 1996, he is staff physicist at LLNL. He became APS Fellow in 2008. He has specialized in theoretical modeling of transition metals, rare-earths, and actinides. He has written chapters for 2 plutonium books, has several review papers on actinide materials, has totally 200 publications and h-index 51. He has 19 LLNL and DOE/NNSA awards and 56 invited presentations since 2000, primarily related to works on actinide theory and modeling. He is Editor for Scientific Reports, and referee for numerous journals.