*From*: uccatvm <uccatvm;at;UCL.ac.uk>*Subject*: Re: CCL:bsse and second derivatives in G98*Date*: Thu, 27 Jan 2000 14:47:29 +0000 (GMT)

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 ====================================================================