The development of the Psi4 open-source quantum chemistry program has focused primarily on density-fitted algorithms for self-consistent-field (SCF) methods like Hartree-Fock and Density Functional Theory (DFT). However, conventional 4-index electron repulsion integral (ERI) algorithms should not be neglected. Recently, we have implemented density screening, an enhancement to the direct SCF algorithm that vets shell quartets of ERIs based on the corresponding blocks in the density matrix. This code was implemented in Psi4, and tested on a variety of molecules and systems, using the cc-pVDZ basis set. For the S22x7 dimer test set, interaction energy errors from using density screening are generally on the order of 10<sup>-4 </sup>kcal/mol, with wall time savings typically ranging from 30-50%. Connecting this enhancement to incremental Fock builds may lead to further savings.

Implementation and assessment of density screening in the Psi4 quantum chemistry program

ACS Spring Meeting 2021

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