NCSI: Phase Stability and Intercalant Ordering in V2O5 Cathodes

Status	Completed
Mentor Name	Hartwin Peelaers
Mentor's XSEDE Affiliation	Research Allocation
Mentor Has Been in XSEDE Community	4-5 years
Project Title	Phase Stability and Intercalant Ordering in V2O5 Cathodes
Summary	We will use cluster expansions, constructed based on density functional theory (DFT) calculations, to investigate the phase diagram upon intercalation of V2O5, a potential cathode material for non-Li-ion batteries, i.e., batteries that use ions such as Na, Mg, Ca, etc. Cluster expansions are required to be able to run large-scale Monte Carlo simulations. These will be used to introduce temperature to the DFT results, so that phase diagrams for different polymorphs and intercalant concentrations can be obtained. This will also allow for voltage profiles to be calculated.
Job Description	The student will create python scripts using the Atomic Simulation Environment (ASE) framework and the CLuster Expansion in Atomic Simulation Environment (CLEASE) python package to construct cluster expansions for different polymorphs of V2O5 and for different intercalated ions. These expansions will be fitted using machine-learning approaches, and will be based on density functional theory (DFT) calculations, as implemented in the VASP package. These calculations will be parallelized using MPI (both the VASP calculations, but also the Monte Carlo simulations). Results will be stored in databases. The student will interact with high-performance computing resources, and will write code to perform all steps: underlying DFT calculations, fitting of cluster expansions using machine-learning approaches, such as compressed sensing, creating Monte Carlo simulations based on the cluster expansions, and scripts to plot and analyze results.
Computational Resources	The DFT calculations will be performed on XSEDE (in particular on PSC Bridges-2), and will be controlled by scripts written in python (via ASE). Such calculations will typically require 1 node (128 cores on Bridges-2) for 4-6 hours. Fitting of the cluster expansions will be done on the student’s computer and/or the local cluster, and subsequent Monte Carlo simulations will be done on XSEDE machines/local cluster.
Contribution to Community	This project will train an undergraduate student in the use of HPC resources to perform computational research on materials properties using first-principles codes. This will increase the student’s knowledge and proficiency in HPC computing and the underlying physics and material science, which are valuable skills. The project scientific goals might lead to better understanding of, and potential improved, battery cathodes for novel non-Li-ion batteries.
Position Type	Apprentice
Training Plan	The student will continue to refine (and apply) knowledge of python coding, further increase background knowledge of solid state physics, thermodynamics, and quantum mechanics, basic linux shell (cd, mkdir, cp, ls, etc.), and interacting with HPC resources (ssh, scp, SLURM, etc.). This learning will occur through 1-on-1 mentoring with the PI (through Zoom and/or in-person). The student will study the intercalation of V2O5 cathodes based on guiding questions. The more experienced the student becomes, the more open questions and tasks will become. This will introduce the student gradually to more aspects of the scientific process (making hypothesis, designing calculations to test these, analyze results, refine hypothesis, and so on). The student will also take part in regular group meetings to learn about other group members' research and discussions about that research.
Student Prerequisites/Conditions/Qualifications	This is a continuation project, and as such the student already possesses (or will by end of summer) all required background (basic solid state physics, thermodynamics, and quantum mechanics) and proficiency with Python and HPC resources, as well as basic understanding of the underlying DFT code. By end of summer student will have applied all acquired skills on a simple test system (Au-Cu alloys), so she will be ready to apply knowledge to a novel system (V2O5 battery cathode)
Duration	Semester
Start Date	09/01/2021
End Date	12/01/2021