Numerical Gradients CCSD(T)

Luke Thomas uccalht at
Mon Nov 10 19:24:16 GMT 2003

I have a question which I hope somebody will be able to help me with.
I am trying to implement a numerical forces calculation using CCSD(T) on a 
 system with 6 geometric variables.
I would like to just calculate the gradient in one variable, without 
calculating the gradient in the other 5.
I have tried setting the step size for the six variables using

Step, r1=0.01, r2=0.0, r3=0.0 ..... ,

but I am not sure where to putr this command so that MOLPRO sees it.

I have tried

forces, numerical, step ....., startcmd=hf
but this does not see the step in r2 as zero.

I have also tried

forces, numerical, startcmd=hf
step, ....

But this does not work either.

If I manage to set a set step size of zero for one variable, will it just 
ignore the variable and not calcualte the gradient, or will it go through 
the whole gradient calculation without a step size. If so, it there a 
specific way to use the force command to calculate a gradient in a 
specified variable.

Many thanks,

Luke Thomas
University College London

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