Has ABACUS implemented the exchange-correlation kernel of the SCAN & r2SCAN functional?

[Zanthoxylum]

Background

The current implementation of DFPT directly calls XC_Functional::v_xc when constructing the perturbation potential. Can DFPT calculations be performed at the SCAN level?

Describe the solution you'd like

Can the SCAN functional be used and the XC_Functional::v_xc be called?

Task list only for developers

• Notice possible changes of behavior
• Explain the changes of codes in core modules of ESolver, HSolver, ElecState, Hamilt, Operator or Psi

Notice Possible Changes of Behavior (Reminder only for developers)

No response

Notice any changes of core modules (Reminder only for developers)

No response

Notice Possible Changes of Core Modules (Reminder only for developers)

No response

Additional Context

No response

Task list for Issue attackers (only for developers)

• Review and understand the proposed feature and its importance.
• Research on the existing solutions and relevant research articles/resources.
• Discuss with the team to evaluate the feasibility of implementing the feature.
• Create a design document outlining the proposed solution and implementation details.
• Get feedback from the team on the design document.
• Develop the feature following the agreed design.
• Write unit tests and integration tests for the feature.
• Update the documentation to include the new feature.
• Perform code review and address any issues.
• Merge the feature into the main branch.
• Monitor for any issues or bugs reported by users after the feature is released.
• Address any issues or bugs reported by users and continuously improve the feature.

[ahxbcn]

As far as I know, the SCAN functional can be used by setting dft_functional to scan directly, but the R2SCAN functionsl should be used via LibXC, and set dft_functional to MGGA_X_R2SCAN+MGGA_C_R2SCAN.