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: Zhigang Mei Applicant's institution: ANL Applicant's division: NE Project Name: DFT_UMo Project title: Fundamental thermophysical properties of U-Mo alloys by DFT Associated funding: DOE NNSA Other Systems: Science: U-Mo based alloys fuels are the most promising fuel for the future high-performance reactors with low-enriched uranium (LEU). As part of a global effort on nuclear non-proliferation, two types of U-Mo fuels with different Mo concentrations, i.e., U-7wt%Mo (U-7Mo) dispersion fuel and U-10wt%Mo (U-10Mo) monolithic fuel, are currently being developed by the European High Density LEU Fuel program and the US High-Performance Research Reactor Fuel Development program (HPRRFD), respectively. However, the accelerated swelling of U-Mo fuel at high burnup raises concern about its applications at high power and burnup. Due to the low solubility of fission gas atoms (mostly Xe and Kr) in U-Mo alloys, fission gases precipitate into gas-filled bubbles, which leads to the fuel swelling as well as overall loss of mechanical strength. Understanding the process of nucleation, growth, migration and coalescence of fission-gas bubble is, therefore, a key aspect to an acc urate prediction of the fuel swelling at high burnup. Mesoscale simulations using approaches such as phase field method plays an important role in the prediction of gas bubble evolution kinetics in U-Mo fuels. However, there are very few studies of the fundamental thermophysical properties of the U-Mo alloy system, which are required for the mesoscale simulations of gas bubbles in U-Mo fuels. Due to the difficulty of treating the f-electrons in uranium and the complexity of describing the disordered structure of the U-Mo alloys, there is no study of the elastic and surface properties of U-Mo alloys from either experiment or theory. To this end, we systematically investigate the elastic and surface properties of the U-Mo alloys using DFT calculations. Project description: We will use density functional theory (DFT) method as implemented in VASP to predict the elastic and surface properties of U-Mo alloys. The special-quasirandom structure (SQS) method as implemented in ATAT will be used to generate a set of system-independent 128-atom-bcc SQSs spanning the entire concentration range, i.e., five different concentrations, in order to simulate the binary random substitutional U-Mo alloys. DFT codes VASP has been extensively tested on LCRC machines, such as Blues and Bebop. Recent test of the latest version of VASP6 shows a good scalability using 16 Broadwell nodes or less on Bebop. My tests on Bebop show that a typical structural relaxation of 128-atom SQS of U-Mo takes 5 hours using 8 nodes and 1 hour for static calculations. For bcc U-Mo alloy, there are 6 symmetrically different surface orientations with a maximum Miller index of 2. For each surface orientation, eight different terminations will be calculated to get better statistics. Therefore, the total cpu-hours for surface energy calculations will be 36*8*6*6*8*5=400000 cpu-hours. In order to get the elastic properties of U-Mo alloys, stress-strain method will be used to calculated the elastic constants. 12 different sets of strains will be applied to the relaxed cubic U-Mo SQS structure to calculate the resultant stresses in order to obtain all the 21 stress tensors. 9 different concentrations of U-Mo alloys together with the two endmembers will be studied in this work. Therefore, the total cpu-hours for elastic property calculations will be 36*8*6*11=200000 cpu-hours. The total cpu-hours needed for this projects are expected to be 600000. Industry partnership: Project URL: Requested allocation: 600000 Q1: 150000 Q2: 150000 Q3: 150000 Q4: 150000 Justification: Recent tests on Bebop show that the latest version of VASP6 can be well scaled to up to 32 Broadwell nodes on Bebop. Storage requirements: 1 TB 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