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##

23.6 CPHF for gradients, expectation values and polarizabilities

The accuracy and other parameters of the CPHF calculations necessary to compute gradients and response properties
can be modified using the `CPHF` directive:

`CPHF`,
[`THRMIN=`*thrmin*],
[`THRMAX=`*thrmax*],
[`MAXIT=`*maxit*],
[`SHIFT=`*shift*],
[*SAVE=record*],
[*START=record*],
[`DIIS=`*idiis*],
[`DISM`=idism]

`THRMIN`
- CPHF convergence threshold (default 1.d-6).
`THRESH` and `ACCU` are aliases for this.
`THRMAX`
- initial CPHF convergence threshold in geometry optimizations. Once the geometry is converged to
a certain accuarcy (depending on
`OPTCONV`), the threshold is stepwise reduced to `THRMIN`.

The default is `THRMAX`=min(1.d-6,`THRMIN`*100); Values larger than 1.d-6 are ignored.
`MAXIT`
- Maxmimum number of iterations (default 50).
`SHIFT`
- Level shift for CPHF (default 0.1).
`DIIS`
- First macroiteration in which DIIS is used (default 1)
`DISM`
- First microiteration in which DIIS is used (default 1; in microiterations the core contribution is frozen).
`SAVE`
- Record on which the CPHF solution can be saved for later restarts. The solution is saved
automatically in geometry optimizations and frequency calculations.
`START`
- Record from which initial guess is read. A starting guess is read automatically in geometry optimizations
and frequency calculations.

In density-fitting MP2, only `THRMIN` is active, the rest of the options are handled automatically.

** Next:** 23.7 Density-fitting MP2 (DF-MP2,
** Up:** 23 MØLLER PLESSET PERTURBATION
** Previous:** 23.5 Polarizabilities and second-order
** Contents**
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molpro@molpro.net 2018-07-18