Subject: bsse and second derivatives in G98

From: Dominik Horinek <[email-masked]>
Date: Thu, 27 Jan 2000 14:28:58 +0100

Hello,

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

Thanks for any help,

Dominik

---

From: uccatvm <[email-masked]>
Date: Thu, 27 Jan 2000 14:47:29 +0000 (GMT)

Hi Dominik,
  
> Ar  -5.3307700 -4.9821510 -5.6341740

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
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     Tanja van Mourik                                                
                                      phone                               
     University College London        work:   +44 (0)171-504-4665   
     Christopher Ingold Laboratories  home:   +44 (0)1895-259-312    
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-- 
  ====================================================================
     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: [email-masked] 
     United Kingdom                   home: [email-masked]     
  ====================================================================