[molpro-user] Intensity of Vibrational Frequencies

[Guntram Rauhut]

Dear Debrashee Manna,

infrared intensities can only be computed for those methods, for which 
analytical gradients are available. This is not the case for CCSD(T). In 
principle there are several solutions to your problem:

1) You may switch from CCISD(T) to QCISD(T). Typically the deviations 
are small, but it depends on the system. In that case your input should 
work.

2) The 2nd option would be to compute the PES at the CCSD(T) level and 
the dipole moment surfaces at the QCISD(T) level. Then you would need to 
change your input to

hf
ccsd(t)
optg
{freq,symm=auto
print,low=50}

label1
{hf
start,atden}
ccsd(t)
etmp=_energy
{qcisd(t)
cphf,1}
energy=etmp

{surf,start1D=label1,sym=auto
  intensity,dipole=2
  disk,where=home,dump='molecule.pot'}
vscf
put,irspec,irspec.gnu

As the generation of the PES for the anharmonic calculations typically 
is quite demanding, I always recommend to dump the PES to disk. For that 
reason I also inserted the DISK directive into your input. You may have 
a look into the manual.

Best wishes,

     Guntram



On 04/25/2013 02:29 PM, Debashree wrote:
> Hello!!
> I want to calculate vibrational frequencies along with their 
> intensities using ccsd(t) method and i am using following options,
>
>
> hf
> ccsd(t)
> optg
> {frequencies,symm=auto
> print,low=50}
>
> label1
> {hf
> start,atden}
> {ccsd(t)
> cphf,1}
>
> {surf,start1D=label1,sym=auto
>   intensity,dipole=2}
> vscf
> put,irspec,irspec.gnu
>                            
> This is giving the frequency values but the intensity values are coming zero.
> Please help me out.
>
> With regards,
> Debashree Manna
>
>
> _______________________________________________
> Molpro-user mailing list
> Molpro-user at molpro.net
> http://www.molpro.net/mailman/listinfo/molpro-user

-- 
********************************************************************************

  Prof. Dr. Guntram Rauhut
  Institut f. Theoretische Chemie
  Universitaet Stuttgart
  Pfaffenwaldring 55
  D-70569 Stuttgart
  Germany

  Tel. :   +49/(0)711/685-64405
  FAX :    +49/(0)711/685-64442
  E-Mail : rauhut at theochem.uni-stuttgart.de
  HTTP :   www.theochem.uni-stuttgart.de/~rauhut/

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