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Details of calculation parameters for the density functional theory (DFT) calculation results contained in the Materials Project (MP) database. |
We use DFT as implemented in the Vienna Ab Initio Simulation Package (VASP) software [1] to evaluate the total energy of compounds. For the exchange-correlational functional, we employ a mix of Generalized Gradient Approximation (GGA) and GGA+U, or a mix of GGA, GGA+U, and r2SCAN. Both mixing schemes are described here. All calculations are performed at 0 K and 0 atm. All computations are performed with spin polarization on and with magnetic ions in a high-spin ferromagnetic initialization (the system can of course relax to a low spin state during the DFT relaxation). For a select number of materials, alternate spin states are searched for. Details on this can be found in the Magnetic Properties section.
Input structures are sourced from many different places, including the Inorganic Crystal Structure Database (ICSD). [2] We relax all cell and atomic positions in our calculation two times in consecutive runs. When multiple crystal structures are present for a single chemical composition, we attempt to evaluate all unique structures as determined by an affine mapping technique. [3]
More detailed information on the GGA/GGA+U and r2SCAN calculations run by the Materials Project can be found in the following two subsections:
{% content-ref url="../materials-methodology/calculation-details/gga+u-calculations/" %} gga+u-calculations {% endcontent-ref %}
{% content-ref url="../materials-methodology/calculation-details/r2scan-calculations/" %} r2scan-calculations {% endcontent-ref %}
[1]: Kresse, G. & Furthmuller, J., 1996. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Physical Review B, 54, pp.11169-11186.
[2]: G. Bergerhoff, The inorganic crystal-structure data-base, Journal Of Chemical Information and Computer Sciences. 23 (1983) 66-69.
[3]: R. Hundt, J.C. Schön, M. Jansen, CMPZ - an algorithm for the efficient comparison of periodic structures, Journal Of Applied Crystallography. 39 (2006) 6-16.