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Previous: Simultaneous vector iteration.
In the iterative method outlined
above, the super-matrices A and B never need to be set up
explicitly; only the products of A and B with some suitable basis
vectors are required. These matrix-vector-products are evaluated
very efficiently in the AO basis, because the required four-index
integrals can be computed ``on the fly'' and need not be transformed
or stored on disk. In addition, prescreening techniques based on
rigorous bounds are straightforward to apply. This leads to a
O(N2) - O(N) for the time-determining
steps. Due to the similarity to ground state fock matrix
construction, the same keywords are used to control these steps as
in semi-direct SCF, namely $thime, $thize,
$scfintunit, see Chapter 6. The same is true
for DFT and RI keywords such as $dft, $ridft,