Inquiry about the implementation details of GGA_GGA+U_R2SCAN mixing in Materials Project

Materials Project
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Dear pymatgen/Materials Project community,

I’ve been exploring the new r2SCAN metaGGA functional approach used in the Materials Project database and have some specific questions regarding the GGA_GGA+U_R2SCAN mixing adjustment.

From the Materials Project website, I understand that “formation energies have now been calculated with the r2SCAN metaGGA functional, which improves the accuracy of reported thermodynamic data.” When examining the data for material mp-3527 (Na₃AgO₂), I noticed:

  1. The GGA_GGA+U_R2SCAN mixed approach shows an energy adjustment described as “MP GGA(+U)/r2SCAN mixing adjustment: 53.6587 eV (4.4716 eV/atom)”

  2. This appears to shift the r2SCAN calculated energy (-8.524 eV/atom) to match the corrected GGA/GGA+U scale (-4.052 eV/atom)

I’d appreciate clarification on:

  1. What is the exact workflow for implementing this mixing scheme? Do you first perform separate GGA/GGA+U and r2SCAN calculations and then apply a post-processing correction?

  2. Is there a standardized approach for calculating the mixing adjustment for different materials, or is it system-dependent?

  3. Is there documentation or code examples available for how to reproduce this mixing approach for my own calculations?

  4. How was this mixing scheme validated, and what improvements in accuracy does it provide over pure GGA/GGA+U or pure r2SCAN calculations?

Thank you for your time. Any insights or pointers to relevant documentation or code would be extremely helpful for my research.

Sincerely,
Zhao

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The mixing scheme between PBE GGA, PBE+U, and r2SCAN calculations is described:

MP only performs PBE+U calculations for oxides / sulfides, so the mixing scheme works to align the convex hulls in four cases:

  • PBE and r2SCAN calculations have been performed
  • PBE+U and r2SCAN calculations have been performed
  • Only PBE calculations have been performed
  • Only r2SCAN calculations have been performed

The mixing / corrections schemes are only applied after DFT calculations have been performed

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