[molpro-user] Mixed derivatives in Numerical Hessian

[Leonid Shirkov]

This is great. Are there any plans to implement MP2 and CCSD(T)
analytical Hessians?
That would improve the accuracy e.g. of high order anharmonic force constants.

On Wed, Feb 8, 2017 at 12:24 AM, Werner Győrffy
<gyorffy at theochem.uni-stuttgart.de> wrote:
> Dear Aleksandr,
>
> I agree that the thresholds must be made tighter: especially for
> Hartree-Fock, and also for CP-HF in the case of using analytical gradients.
> One should be careful not to set the thresholds too tight. For example, the
> suggested "gthresh,orbital=1.0d-10" is equivalent to "{hf;accu,20;}" which
> seems to be unnecessary low and might cause convergence problems.
>
> Yes, MP2 and DF-MP2 Hessians are computed by using analytical first
> derivatives.
>
> CCSD(T) analytical gradients have been already implemented in the
> development version of Molpro. It will be hopefully available soon in the
> next release.
>
> Regards,
>
> Werner.
>