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: Anh Ngo Applicant's institution: ANL Applicant's division: MSD Project Name: ReNiO3 Project title: Structural Evolution of rare earth nickelates under high pressure conditions Associated funding: BES Other Systems: Science: Rare earth nickelates with the specific formula ReNiO3, where Re is a rare earth metal, exhibits exotic physical properties and have attracted a lot of research interest. It shows a sharp insulator to metal transition, which is not well understood. Further to this, in the insulating phase Ni exhibits a complex antiferromagnetic ordering below the Néel temperature and the oxygen octahedra around Ni positions are significantly distorted, which leads to the manifestation of Jahn-Teller effect. The distinct Ni-O bond distances observed for Ni atoms also suggest the presence of a charge disproportionation effect. Computational efforts are needed to gain insight into different mechanisms of structural and electronic transitions with applied pressure. In this study, we plan to address how the structure and electronic properties of ReNiO3 change under high pressure effects. Using density functional theory and Green function calculations, we will calculate structure and spectra to compare to x-ray experiments done at the APS. We will focus on interpretation of the results that can help to better understand metal-insulator transition. This study will provide fundamental information on electronic properties of the important class of complex oxides and guide the ongoing experimental efforts at the APS. Project description: Structure optimizations of ReNiO3 (~80 atoms) with different magnetic configurations will be carried out using (2 x 1x 2) bulk unit cells. By comparing different magnetic ordering energies we will conclude which configuration corresponding to the ground state energy. Once ground state structure is found we will go on to address the structural dependence of ReNiO3 under high pressure. We intend to carry out the density functional theory (DFT) calculations using the VASP package. Periodic boundary condition (PBC) will be imposed in order to maintain periodicity of the solid support. Gradient corrected PBE density functional will be used for these calculations. Those programs are currently available on Blues cluster and scale reasonably well on parallel processors. Energy optimization of ReNiO3 (~80 atoms contain 16 Ni with different spin configurations) using GGA+U takes approximately 4608 CPU hours (16*6*48) and we plan roughly 60 of such calculations. For pressure calculations, since ReNiO3 is a correlated complex oxide, we will perform density functional theory (DFT) calculations using the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional and performed the atomic relaxations within the unit cells. This takes roughly 4608 CPU hours (16*6*48) and we plan to run 80 of these calculations. To investigate metal-insulator transition we plan to run additional 66 HSE calculations for the density of state (DOS) at the ambient pressures of 0 GPa to 3.4 GPa. So our total request is 60*4608 + (80+66)* 4608 =949248 core hours. Industry partnership: Project URL: Requested allocation: 950000 Q1: 200000 Q2: 250000 Q3: 250000 Q4: 250000 Justification: VASP package is widely used on Blues and its scaling is well documented. Storage requirements: 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