# Supporting Data for "Multi-Step Oxygen Redox Mechanism in the Polyanionic Lithium-Rich Cathode Li2FeSiO4" Authors: - Patrick J. Taylor, ORCID: 0009-0003-6511-6442 - Kit McColl, ORCID: 0000-0002-7794-8276 - M. Saiful Islam, ORCID: 0000-0002-8077-6241 - Benjamin J. Morgan, ORCID: 0000-0002-3056-8233 This archive contains the complete raw dataset from which all results in the article "Multi-Step Oxygen Redox Mechanism in the Polyanionic Lithium-Rich Cathode Li2FeSiO4", *J. Am. Chem. Soc.* (https://doi.org/10.1021/jacs.6c02850), are derived. The analysis code that regenerates the figures and results is in a companion repository on GitHub (https://github.com/PatrickJTaylor/data_Li2FeSiO4), together with the minimal subset of this data that the code requires (`extracted_data`). That subset can be regenerated from this archive with the `extract.py` script. ## Usage `extract.py` requires numpy, pymatgen and tqdm. The script includes PEP 723 inline metadata, so it can be run with a version-pinned environment using uv (https://docs.astral.sh/uv/getting-started/installation/): ```shell uv run extract.py ``` Before running the script, download `hull.tar.gz`, `molecular_dynamics_500K.tar.xz`, `molecular_dynamics_1000K.tar.xz`, `polymorph_stability.tar.gz`, `sequential_delithiation.tar.gz` and `thermodynamic_stability.tar.gz`, and extract them all into the same directory. ## Directory structure ### hull DFT relaxations of (inverse Pmn2_1) LixFeSiO4 configurations, used to compute the convex hull and voltage curve in Fig. S2. `1x1x1` contains every LixFeSiO4 configuration that can be enumerated in the conventional cell (LixFe2Si2O8); `2x1x1` and `2x2x1` contain randomly generated configurations in the corresponding expansions of the conventional cell. `hull/Li` contains a relaxation of the metallic Li primitive cell, used to compute the voltage curve. ### molecular_dynamics/500K and molecular_dynamics/1000K The AIMD trajectories at 500 K (`molecular_dynamics_500K.tar.xz`) and 1000 K (`molecular_dynamics_1000K.tar.xz`). `equilibration` contains the equilibration run. `production` contains the production trajectory, split into one subdirectory per HPC job. `selected_frames` contains one subdirectory for each frame selected from the trajectory, named by its index in the production trajectory. Each selected frame contains: - `pre-relaxation` and `relaxation`, a two-step DFT geometry optimisation of the frame (the first with reduced settings); - `lobster`, a static DFT calculation at the relaxed geometry, followed by the LOBSTER analysis; - `wannier`, the Wannierisation used to assign oxidation states (see Additional notes). ### molecular_dynamics/initial_relaxation A DFT relaxation of (inverse Pmn2_1) FeSiO4, used to initialise both AIMD simulations (`molecular_dynamics_init_relaxation.tar.gz`). ### polymorph_stability DFT relaxations of LixFeSiO4 at x = 2 and 0 for the polymorphs most common in LixMSiO4 (M = Co, Fe, Mn, Ni) systems: inverse Pmn2_1, P2_1, Pbn2_1, Pmn2_1, Pmnb and P2_1/n (see the Supporting Information of the article). ### sequential_delithiation DFT relaxations, PDOS and ICOBI calculations, and Wannierisations for (inverse Pmn2_1) LixFeSiO4 at x = 2, 1 and 0. ### thermodynamic_stability DFT relaxations of Fe2O3, SiO2 and O2, used to compute the thermodynamic stability of (inverse Pmn2_1) FeSiO4. ## Included files ### VASP Every VASP calculation includes: - `INCAR`, the input parameters - `POSCAR`, the input geometry - `OUTCAR`, the human-readable output - `vasprun.xml`, the machine-readable output The AIMD simulations also include: - `KPOINTS`, the k-point specification - `OSZICAR`, the energy at each timestep - `XDATCAR`, the geometry at each timestep POTCAR files are not included, as they are licensed as part of VASP; the PAW datasets used are identified in each `OUTCAR`. ### LOBSTER Every LOBSTER calculation includes: - `KPOINTS`, copied from the IBZKPT file written by the preceding static DFT calculation - `lobsterin`, the LOBSTER input - `lobsterout`, diagnostic output, including the spilling factor - `ICOBILIST.lobster`, the ICOBIs, by atom pair and spin channel - `projectionData.lobster`, the coefficient matrices from which LOBSTER computes the DOS, COHP, COBI, etc. The calculations for sequentially delithiated LixFeSiO4 also include `DOSCAR.lobster`, the projected density of states. ### Wannier90 Every Wannier90 calculation includes (with `` = `1` for spin up, `2` for spin down): - `wannier90..wout`, diagnostic output, including the spread of each Wannier function - `wannier90._centres.xyz`, the Cartesian position of each Wannier centre For the selected AIMD frames, the `.wout` files are gzip-compressed. The Wannierisations of the lowest unoccupied states in sequentially delithiated LixFeSiO4 also include `wannier90._.xsf`, the isosurface data for Wannier function XXXXX. ## Additional notes ### Selected-frame energies and magnetic states The relaxed-frame energies, Fe magnetic moments and ICOBIs reported in the article are all taken from the static calculation in each frame's `lobster` subdirectory, not from the final step of the relaxation. These static calculations use tetrahedron-method Brillouin-zone integration (`ISMEAR = -5`). Oxygen atoms belonging to O-O dimers are initialised with a small negative magnetic moment (see `MAGMOM` in the corresponding `INCAR`). For frame 12276 of the 1000 K trajectory, a static calculation started from scratch converges to a metastable magnetic state 0.90 eV higher in energy than the state reported in the article. The static calculation included here was instead restarted from an existing wavefunction (`ISTART = 1`, `ICHARG = 0` in the `OUTCAR`), and converges to the same magnetic state as the relaxation (total magnetisation 150 Bohr magnetons). The static calculations for all other frames start from scratch (`ISTART = 0`, `ICHARG = 2`). ### Wannierisation Each `wannier` subdirectory contains three stages: 1. `scf`, a static DFT calculation with a full (unsymmetrised) k-point mesh; 2. `scdm`, an SCDM calculation that generates the initial guess for localisation; 3. `localisation`, the Wannier90 calculation of the maximally localised Wannier functions. Stages 2 and 3 are repeated for each spin channel, in `up` and `down` subdirectories. For sequentially delithiated LixFeSiO4, `wannier` has an additional level: `oxidation_states` (used to assign oxidation states) and `LUMO` (used for the isosurfaces in Fig. 4). ### Patched VASP for SCDM A small number of SCDM calculations were performed with a custom-patched version of VASP 6.5.1, which adds the option `CUTOFF_TYPE = energy_range`. With this option, `CUTOFF_MU` and `CUTOFF_SIGMA` become strict lower and upper bounds on the energies of the Bloch states included in the quasi-density matrix. VASP does not currently provide a way to select Bloch states within a strict energy window: `CUTOFF_TYPE = gaussian` can approximate one, but when the states of interest lie close in energy to other bands it is difficult, and sometimes impossible, to exclude the unwanted states. We used the patch to compute Wannier functions for the lowest unoccupied states of Li2FeSiO4 and FeSiO4. The patch itself is not included in this archive.