Hello, A new project on the LCRC cluster has been requested. Please forward the information on to the LCRC Allocation sub-committee. Applicant's name: Peter Zapol Applicant's institution: ANL Applicant's division: MSD Project Name: chemexp Project title: Chemical Expansion in Perovskites Associated funding: DOE BES Other Systems: none Science: The solid oxide fuel cell (SOFC) presents a highly attractive energy conversion option besides the conventional energies as a clean and efficient energy conversion technology. However, the high operating temperature limits its commercial applications. The LaxSr1-xCoyFe1-yO3-delta (LSCF) displaying mixed ionic electronic conductivity serves as a promising cathode material for intermediate-temperature SOFCs. For the LSCF perovskite materials, the oxygen stoichiometry plays a critical role in the materials performance characteristics. Recently experiments showed that the oxygen stoichiometry can be tuned by applying electrical potentials across the LSCF/YSZ (yttria-stabilized zirconia) heterostructures. However, the large change in the oxygen vacancies leads to a significant dilation or contraction of the lattice known as chemical expansion. This phenomenon of lattice change with the applied voltage is also reported in La0.8Sr0.2CoO3-delta (LSCO) mater ials. Understanding the lattice changes with the bias voltage is critical because the large stresses induced by the changing lattice may lead to failure operation of the SOFC. To the best of our knowledge, there is no good explanation on the lattice changes with the applied voltage yet. Collaborating with the experimentalists at Argonne, we will carry out a series of researches to compare and explain the experiment results. Project description: Part of our work is employing density functional theory to explore the lattice changes with the oxygen stoichiometry and the oxygen vacancy migration across the LSCF/YSZ interface and in the bulk LSCF. The projector augmented plane-wave method as implemented in the Vienna ab initio simulation package (VASP) will be employed to find the optimized structure of each oxygen vacancy configuration. VASP is a well validated code which is installed at LCRC and is widely used for this type of calculations with good performance. We will use the climbing image nudged elastic band method (NEB)to do research on the oxygen vacancy migration. We have done some test calculations on system with 40 atoms to find the optimized structures using 32 cores. The calculation works very well, as expected. We plan to do calculations of different oxygen vacancy concentrations corresponding to deviation from formal oxygen stoichiometry of 3 by 0.075, 0.125, 0.25, 0.375, 0.5. For each configuration, we need several calculations to find the optimized ionic positions at fixed in-plane lattice constant. In each calculation, we need about 15 hours of run time when using 32 cores. For the oxygen vacancy migration, each NEB calculation is about 20 hours using 32 cores. We need to calculate about 5 NEB points, 10 pathways for the different 5 oxygen vacancy concentrations. Therefore, expected time estimate for structural optimizations is (8 cores/node * 4 nodes * 15 hours of run time * 50 different runs) 24,000 core-hours and for NEB calculations is (8 cores/node * 4 nodes * 20 hours of run time * 250 different runs)=160,000 core-hours.We also want to do some tests on larger system sizes, which adds about 15,000 core hours. The total time requested is about 200,000 core hours. There will be two to three members in the project. Industry partnership: none Project URL: Requested allocation: 200000 Q1: 0 Q2: 40000 Q3: 80000 Q4: 80000 Justification: Storage requirements: default storage allocation is sufficient The requester has used undetermined amount hours of their initial startup project. In addition to approving an initial amount, please specify a Category and Subcategory for this project. For a list of the current selection of approved categories, please see: https://wiki.lcrc.anl.gov/wiki/Processes/Categories Once the Allocation committee has approved the project, please go to the Project Management page to create it: https://accounts.lcrc.anl.gov/projects.php Thank You, The LCRC Accounts System