Usage: put the "ris.bas" or "ris+p.bas" file in the working directory, and use this script to run TDDFT-ris calculation.

The SCF part is same any usual SCF calculations. In the TD part, the script uses the user-define minimal JK fitting basis , "ris.bas", and turned off the XC kernel. I would not expect TDDFT-ris has too much speedup compared with RIJCOSX in ORCA, becasue COSX is N^3 and ris (RIJK) is N^4. I only observed a factor of 4 speedup in a 38 atoms system with def2-TZVP basis.

However, TDDFT-ris (and its variant, rid) was originally developed as the initial guess and preconditioner to help Davidson algorithm in TDDFT converge faster. There are many tricks to further speedup the TDDFT-ris itself, such as truncating the high energy obital pairs in the exchange term (not the Coulomb term), so that the initial guess and preconditioner is cheap enough to really help reduce the overall TDDFT cost.

Reference,

1. Zhou, Zehao, and Shane M. Parker. "Converging Time-Dependent Density Functional Theory Calculations in Five Iterations with Minimal Auxiliary Preconditioning." Journal of Chemical Theory and Computation (2024).
2. Zhou, Zehao, Fabio Della Sala, and Shane M. Parker. "Minimal auxiliary basis set approach for the electronic excitation spectra of organic molecules." The Journal of Physical Chemistry Letters 14, no. 7 (2023): 1968-1976.
3. Zhou, Zehao, and Shane M. Parker. "Accelerating molecular property calculations with semiempirical preconditioning." The Journal of Chemical Physics 155, no. 20 (2021).