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##

Fast geometry optimizations with RI-SCF based gradients

If geometry optimizations on MP2 or CC2 level are performed
with large basis set, especially with diffuse basis functions,
the -steps might become the dominant part of the
overall timings.
In these cases, the integral screening in the
Hartree-Fock part often becomes inefficient.
The resolution-of-the-identity can be applied here to speed up
the calculation of the HF reference wavefunction, as well as
the solution of the coupled-perturbed Hartree-Fock (CPHF) equations
in the MP2 or CC2 gradient calculation.
An additional auxiliary basis (denoted `jkbasis`)
set has to be assigned via
the General Options Menu in the `define` program.
In the submenu `rijk` choose `on` and select
your auxiliary basis set.
Then, run the `jobex` script the additional rijk-flag:

> jobex -level cc2 -rijk

Note, that it is at the moment not possible to perform these calculation
parallel because the RI-JK approximation is presently not supported
in the parallel version of the `ridft` program.

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** Up:** First-Order Properties and Gradients
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