Pyrochlore Compounds From Atomistic Simulations

Abstract

Pyrochlore compounds (A2B2O7) have a large applicability in various branches of science and technology. These materials are considered for use as effective ionic conductors for solid state batteries or as matrices for immobilization of actinide elements, amongst many other applications. In this contribution we discuss the simulation-based effort made in the Institute of Energy and Climate Research at Forschungszentrum Jülich and partner institutions regarding reliable computation of properties of pyrochlore and defect fluorite compounds. In the scope of this contribution, we focus on the investigation of dopant incorporation, defect formation and anion migration, as well as understanding of order-disorder transitions in these compounds. We present new, accurate simulated data on incorporation of U, Np, Pu, Am and Cm actinide elements into pyrochlores, activation energies for oxygen migration and radiation damage-induced structural changes in these materials. All the discussed simulation results are combined with available experimental data to provide a reliable description of properties of investigated materials. We demonstrate that a synergy of computed and experimental data leads to a superior characterization of pyrochlores, which could not be easily achieved by either of these methods when applied separately.

Fundamentals of energy storage from first principles simulations: Challenges and opportunities

“…Steady advancements in high performance computing and computational software enable investigation of complex systems containing hundreds of atoms from first principles (Jahn and Kowalski, 2014). Over the past decade, ab initio methods have been intensively applied, including our own studies, for computational investigation of various classes of energy materials, including these of importance in electrochemistry, energy storage and nuclear energy production, delivering information on: the structural (Rustad, 2012;Feng et al, 2013;Blanca-Romero et al, 2014;Beridze et al, 2016;Connor et al, 2021), the electronic structure (Blanca-Romero et al, 2014;Kowalski et al, 2017a;Lee et al, 2017;Kowalski et al, 2021;Murphy et al, 2021;Cui et al, 2022;Tesch and Kowalski, 2022), the elastic (Wang et al, 2005;Feng et al, 2013;Ali et al, 2016;Ji et al, 2017a;Kowalski et al, 2017b), the thermodynamic (Mogilevsky, 2007;Feng et al, 2013;Li et al, 2014;Kowalski et al, 2015;Ji et al, 2017b;Neumeier et al, 2017b;Eremin et al, 2019;Kowalski et al, 2021), the thermochemical (Rustad, 2012;Beridze et al, 2016;Kowalski, 2020) parameters, properties of electrochemical interfaces (Krishnamurthy et al, 2004;Lee et al, 2017;Tesch et al, 2021) and the radiation damage resistance Ji et al, 2017c;Jolley et al, 2017;Cui et al, 2022), to name but a few. Energy materials often contain d and f elements (e.g., transition metals (TM), lanthanides (Ln), actinides (An)), which play an active part in determining the materials properties.…”

Atomic Insights into the Structural Properties and Displacement Cascades in Ytterbium Titanate Pyrochlore (Yb2Ti2O7) and High-Entropy Pyrochlores

“…Pyrochlores have cubic fluorite-type structures containing 5 or more elements with oxygen-deficient vacancies having A 2 B 2 O 7 type structure with A (rare-earth) and B (transition metal) being different cations [42,43]. The 'A' position coordinated with 3 + cation atoms while the 'B' position coordinated with 4 + cation atoms, e.g., 3 + cations (La 3+ , Nd 3+ , Gd 3+ , Sm 3+ , and Y 3+ ) and 4 + cations (Zr 4+ , Ti 4+ , and Mo 4+ ) [44].…”

“…This difference is due to the fact that high-entropy alloys have a more complex structure. This complexity can lead to higher Ed due to strong bonding, defects, and strains [43,47,69,70]. The calculation of the threshold energy (E d ) of high-entropy pyrochlore YbYTiZrO 7 was formed by doping the Y element at the A site and the Zr element at the B site.…”

“…This difference is due to the fact that high-entropy alloys have a more complex structure. This complexity can lead to higher E d due to strong bonding, defects, and strains [43,47,69,70]. As the energy of the initial PKA increases, the total number of defects of various atoms increases due to an increase in the mean free path between atoms.…”

Advances and perspectives of actinide chemistry fromex situhigh pressure and high temperature chemical studies

“…2 However, as contemporary studies have highlighted 3 limitations still remain in executing correct standalone calculations without the aid of experimental data to benchmark obtained results. [4][5][6][7][8][9] Consequently, to correctly understand chemical bonding in actinide compounds requires controlled experimental approaches that can both directly probe and examine their limitations in a systematic form. Ex situ HP/HT experimental methods have subsequently formed a powerful means to achieve this and advance fundamental chemical insight.…”