[‘GGA_GGA+U_R2SCAN’] vs. [‘R2SCAN’]

Materials Project
1

Hello everyone,

I’m seeking clarification on the distinction between thermo_types=['GGA_GGA+U_R2SCAN'] and thermo_types=['R2SCAN'] in the data query. I conducted a test on Ag2O using the following query methods:

output1 = mpr.thermo.search(material_ids=[‘mp-353’], thermo_types=[‘GGA_GGA+U_R2SCAN’])
output2 = mpr.thermo.search(material_ids=[‘mp-353’], thermo_types=[‘R2SCAN’])

The formation energy per atom retrieved from output1 is -0.314, whereas from output2 it is -0.169. Could someone shed light on this discrepancy? I’m particularly interested in building an R2SCAN-based Pourbaix diagram in the subsequent steps, but I’m uncertain about which thermo_types to select.

Any insights would be greatly appreciated.

Thank you.

2

@siwen_wang GGA_GGA+U_R2SCAN refers to our mixing scheme correction allowing comparisons between calculations of all three of those types. This docs page may help: Phase Diagrams (PDs) - Materials Project Documentation

– Jason

3

@munrojm Thanks Jason for your information. I’d like to confirm: Is the energy retrieved from ['GGA_GGA+U_R2SCAN'] already corrected to ensure comparability with GGA/GGA_U, while the energy from ['R2SCAN'] remains uncorrected? If that’s the case, is there any way to query uncorrected ['R2SCAN'] data? I attempted to query a ternary metal oxide, such as the Sb-Ag-Co-O system, and it appears that only calculations from ['GGA_GGA+U_R2SCAN'] are available, with no associated results from ['R2SCAN'].

The method I used to query data is

mpr.thermo.search(chemsys=‘Co-Sb-Ag-O’, thermo_type=[‘R2SCAN’], fields=[‘material_id’])

4

@siwen_wang yes, you are correct. The energy retrieved in the GGA_GGA+U_R2SCAN case is already corrected to ensure mixing compatibility, while the R2SCAN data is the raw uncorrected energy from the available R2SCAN calculation.

Unfortunately, it looks like not all materials in that chemical system have R2SCAN calculations. One way to check all available calculations for a given material (or set in a particular chemical system) is to query the materials endpoint and ask for entries:

docs = mpr.materials.search(chemsys='Co-Sb-Ag-O', 
                            fields=["material_id", "entries"])

– Jason

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