Such links as well as general methods are absent.

Hello Verma,

IRC in Gaussian sometimes has numeric problem with algorithm. One solution is in the option of recorrect option select never (or see guassian webpage for other options that could interest in your case).

I hope it helps you,

Joaquim Rius

http://www.gaussian.com/g_tech/g_ur/k_irc.htm

A few more details about the reactions you want to calculate could be helpful to identify the problem.

However, in general you would calculate a catalysed reaction the same way you calculate any other reaction, but you'd have to break down the whole sequence into the individual elemental steps. This can somewhat problematic since these steps aren't always mechanistically well understood.

Dear Simon

Sir I have problem in the understanding of making catalyst cluster and the surface reaction on them. Any way I haven't done any job yet bcoz I ain't getting the idea as many authors have different-2 clusters.

Since I didn't find any tutorial on catalytic reaction that's why I ain't aware of how to find out the active sites etc.

Do we have any general procedure to make the cluster?

Thanks in advance

Do you mean with "catalyst cluster" a cluster of metal atoms? Or simply the complex of (a molecular) catalyst and your substrate?

Dear Simon

I've problem with the complex of cluster with substrate. 

And one more problem is with support like Pt on Al2O3.

Thanks Sir

Unfortunately, there is no simple, cookie-cutter solution for that. Ideally, you can find experimental or at least accepted theoretical data on the structure of these complexes, that you can use as basis to model them. If that's not possible, you'll have to make an educated guess how these complexes might look like – or actually more than one, if you want to make sure you've found a reasonable structure.

But as I said: this is not a trivial problem, since the mechanistic details of some catalytic reactions are poorly understood – and that includes the structure of the substrate/catalyst complexes.

For your problem with aluminium oxide supported platinum, there is experimental data, for instance here: http://w0.rz-berlin.mpg.de/hjfdb/pdf/210e.pdf

Reactions on these systems – and especially calculations of reactions on them – are not my expertise, but as far as I know, normally you can get away with only modelling a slab of your metal surface based on the known structural parameters.

Thanks Simon