# [molpro-user] Trouble computing nonadiabatic couplings with DDR

Terry Frankcombe tjf at rsc.anu.edu.au
Thu Jul 30 04:49:00 BST 2009

```I haven't looked closely at the orbitals you're using, but we have found
that this type of thing can happen if the orbitals do not form a totally
symmetric set.  By that I mean if you include some p orbitals but not
the complete shell, the wavefunction can develop some directionality
which gets picked up in the starting vectors for subsequent
calculations.

Something to consider.

On Wed, 2009-07-29 at 22:34 +0200, Robert Send wrote:
> Dear Molpro-users,
>
> I am trying to compute nonadiabatic coupling vectors with the input
> script below, using the DDR method. However, depending on whether or
> not I compute the couplings at bond distance r=0.5 before the rest of
> the distances (1.0,2.0,3.0,4.0), I get different results. In other
> words,
> r=[0.5,1.0,2.0,3.0,4.0]
> gives different couplings from
> r=[1.0,2.0,3.0,4.0].
>
> I tried to stick as close as possible to the LiF input script from the
> molpro online manual.
>
> Thanks a lot for your help,
>
> Robert
>
> Here comes the input:
>
> memory,160000000
> basis,h=aug-cc-pvdz     r=[1.0,2.0,3.0,4.0]
> dr=0.001               geometry={
> x,y
> h
> h,h,rbh
> }
>
> hf
>
> do i=1,#r             rbh=r(i)          hf
>
>     {casscf
>     closed
>     occ,10,4,4,0
>     wf,2,1,0
>     state,2,1,2
>     orbital,2140.2
>     }
>
>    {ci;
>    wf,2,1,0
>    state,2,1,2   noexc            save,6000.2;    dm,8000.2}
>
>    rbh=r(i)+dr
>
>     {casscf
>     closed
>     occ,10,4,4,0
>     wf,2,1,0
>     state,2,1,2
>     start,2140.2
>     orbital,2141.2
>     }
>
>    {ci;
>     wf,2,1,0
>     state,2,1,2
>     noexc;
>     save,6001.2}
>
>    {ci;trans,6000.2,6001.2;       dm,8100.2}
>
>     rbh=r(i)-dr
>
>    {casscf
>     closed
>     occ,10,4,4,0
>     wf,2,1,0
>     state,2,1,2
>     start,2140.2
>     orbital,2142.2
>     }
>
>    {ci;
>     wf,2,1,0
>     state,2,1,2
>     noexc;save,6002.2}
>
>    {ci;trans,6000.2,6002.2;         dm,8200.2}
>
>    {ddr,dr,2140.2,2141.2,8100.2}    nacme1p(i)=nacme
> {ddr,-dr,2140.2,2142.2,8200.2}   nacme1m(i)=nacme
>
>    {ddr,2*dr                         orbital,2140.2,2141.2,2142.2;
> density,8000.2,8100.2,8200.2}     nacme2(i)=nacme
>
> end do
>
> nacmeav=(nacme1p+nacme1m)*0.5
> for H2
>
> ---------------------------------------
>
> Robert Send
> Theoretische Chemie
> Institut für Physikalische Chemie
> Universität Karlsruhe
>
> +49-721-608-8344
>
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--
Dr. Terry Frankcombe
Research School of Chemistry, Australian National University
Ph: (+61) 0417 163 509    Skype: terry.frankcombe

```