Re: CCL:bsse and second derivatives in G98

Hi Dominik,
 > I'm trying to calculate the hessian of a cluster containing an organic
 > molecule (formic acid) and an argon atom. To account for the bsse I have
 > to do the calculation with ghost atoms for the organic molecule and
 > electrons only at the argon atom. Unfortunately, with G98 this type of
 > calculation fails: 'Molecule is non-linear but NTrRo=3'. Who knows how
 > to fix this problem, or is there another convenient way to obtain the
 > second derivatives without this problem. I used the following input:
 >
 > %Mem=12000000
 > %chk=cluster_1.chk
 > # 6-311++G** MP2=Direct Freq Massage
 >
 >  *cluster 1*
 >
 > 0   1
 >  C   0.0000000  0.0000010 -0.0000110
 >  O   0.0000000 -1.1524620 -0.3291650
 >  H   0.0000000  0.3427030  1.0490010
 >  O   0.0000000  1.0156520 -0.8967590
 >  H   0.0000000  1.8484450 -0.4113800
 > Ar  -5.3307700 -4.9821510 -5.6341740
 >
 >    1  Nuc  0.0
 >    2  Nuc  0.0
 >    3  Nuc  0.0
 >    4  Nuc  0.0
 >    5  Nuc  0.0
 What you are trying to do here is to calulate the frequency of the Ar
 atom (albeit with some basis functions on the formic acid ghost atoms).
 This is not possible.
 Similarly, you cannot calculate the frequencies of formic acid in the
 presence of ghost functions like this (i.e. by replacing the last 5 lines
 by "6 Nuc 0.0"). To calculate a hessian, your molecule has to be in
 the minimum
 (for the given method/basis), and this is not the case (I assume the geometry
 above comes from an optimization on the cluster).
 I am afraid that there is not an easy way to calculate counterpoise-corrected
 frequencies automatically. You would need a potential energy surface and
 calculate the frequencies on it numerically, but this is not practical on any
 higher level of theory.
 Best regards,
 Tanja
 --
   ====================================================================
      Tanja van Mourik
                                       phone
      University College London        work:   +44 (0)171-504-4665
      Christopher Ingold Laboratories  home:   +44 (0)1895-259-312
      20 Gordon Street                 e-mail
      London WC1H 0AJ                  work: T.vanMourik;at;ucl.ac.uk
      United Kingdom                   home: tanja;at;netcomuk.co.uk
   ====================================================================
 --
   ====================================================================
      Tanja van Mourik
                                       phone
      University College London        work:   +44 (0)171-504-4665
      Christopher Ingold Laboratories  home:   +44 (0)1895-259-312
      20 Gordon Street                 e-mail
      London WC1H 0AJ                  work: T.vanMourik;at;ucl.ac.uk
      United Kingdom                   home: tanja;at;netcomuk.co.uk
   ====================================================================