Combining The Advantages Of Semi-Direct Schemes And Linear-Scaling Self-Consistent Field Methods

A new stored-integral self-consistent field (SCF) scheme is presented for both Hartree-Fock (HF) and density-functional theory (DFT), which combines the advantages originally attributed to the direct and also linear-scaling SCF methods with those of traditional indirect or semi-direct approaches. By storing the density-screened two-electron integrals in the first time-consuming SCF iteration, recalculation of integrals can be almost avoided in subsequent iterations as the one-particle density matrix is shown to be quite representative for the one in later iterations. For the dominant exchange-type contractions, speed-ups of typically 1.5-3.7 are observed.