Polyanion sodium cathode materials dataset

We have created a database that includes structures optimized to the lowest energy (ground-state structures), ab initio molecular dynamics simulations trajectories sampled at 1000K, and structures sampled from ML-driven molecular dynamics simulation at 1000K using active learning algorithms. This is sampled for four sodium ion polyanionic cathode materials NaTMPO₄(olivine) ,NaTMPO₄(maricite), Na₂TMSiO₄ and Na_2.56TM_1.72(SO₄)₃ , along with various structures incorporating doping of transition metal ions (TM). We consider four different transition metal ions (Fe, Mn, Co, Ni). The dataset consist of 113,703 structures.

For each sampled structure, we record its crystal composition, total energy, atom-wise force vectors, atom-wise magnetic moments derived from Mulliken analysis, and atomic charges obtained through Bader analysis. Our polyanionic Sodium ion battery database serves as a valuable addition to existing datasets, enabling the exploration of phase space while providing insights into the dynamic behavior of the materials.

For the sampling density functional theory (DFT) calculation were performed using the Vienna Ab initio simulation package (VASP) version 6.4. The Perdew-Burke-Ernzerhof (PBE) functional with Hubbard-U corrections were applied was utilized for all calculations. The U-values are similar to the ones used for materials project (Fe: 5.3eV, Mn: 3.9eV, Co: 3.32eV, Ni: 6.2eV). For all calculations, an energy cutoff of 520eV was applied, with a smearing width of 0.01eV and convergence criteria set to 1e-5eV for energy and 0.03eV/Å for forces. All calculations were performed with spin polarization. The k-points employed for the four materials were fixed, with NaTMPO₄(olivine) and NaTMPO₄(maricite) utilizing [3,4,6] gamma points, Na₂TMSiO₄ employing [3,4,4] gamma points and Na_2.56TM_1.72(SO₄)₃ utilizing [2,3,4] gamma points. When constructing supercells, the gamma point in the direction of cell enlargement was halved.

All molecular dynamics (MD) simulations are conducted using the Langevin thermostat with a friction constant of 0.003. The temperature is maintained at 1000K to facilitate diffusion events, and a time step of 1fs as employed throughout the simulations. All simulations are executed within the canonical (NVT) ensemble and a sample frequency was set to 1fs.

The dataset is presented in XYZ format. The dataset is divided into single transition metal ions structures and multiple transition metal ion structures. This division is provided for each of the four cathode materials: NaTMPO₄(olivine) ,NaTMPO₄(maricite), Na₂TMSiO₄ and Na_2.56TM_1.72(SO₄)₃ . For example, Na_2.56TM_1.72(SO₄)₃ structures are split into single transition metal ion types Na2M2SO4_alluadite_single.xyz and multiple transition metal ion types Na2M2SO4_alluadite_multiple.xyz. The combined dataset, consisting of 113,703 structures, is available in Combined.xyz.
To extract structural compositions and physical properties, the ase.io.read function from ASE version 3.23.0 is used. An example of how to extract data and plot the physical properties is provided in https://github.com/dtu-energy/cathode-generation-workflow/tree/main/extract_data/read_data.py and https://github.com/dtu-energy/cathode-generation-workflow/tree/main/extract_data/utils.py contains two functions, one used to attached Bader charges to an ASE atom object an another to combine multiple XYZ data files.
To cite the data please use the doi https://doi.org/10.11583/DTU.27202446