[molpro-user] CCSD(T) RHF not converging

Jörg Saßmannshausen jorg.sassmannshausen at strath.ac.uk
Wed Jul 29 20:32:32 BST 2009

Hi Gerald,
thanks for your reply.

> Did you check if your geometry is correct? 

I have a converged geometry at the mp2/6-31g* level of theory with no 
imaginary frequencies. So I would consider that as 'correct'.

> Angstrom/Bohr-conversion issues 
> might be a problem. Molpro will print the geometry parameters (e.g., bond
> lengths) in both Angstroem and Bohr, and you should check if they are
> sound. It is *very unlikely* that Molpro's RHF will fail to converge a
> reasonable closed-shell organic compound. I don't think I've ever seen that
> happening.

I was using the cartesian coordinates as supplied by Molden. So I would have 
thought it is ok. 
By the way, it finally converged with 125 steps.

> Some other things to consider:
> http://www.molpro.net/pipermail/molpro-user/2008-January/002379.html
> > I have tried to set it to a (rediculus) high number of 300
> > with the MAXIT keyword, but somehow that seems to be ignored.
> "maxit" is not a keyword. It is either a parameter or an option. So you
> generally need to use either
>   {progname,maxit=100}
> or
>   {progname;maxit,100}
> Unfortunately there are still some inconsistencies, with some programs
> accepting only the first form, some only the second, and some accepting
> both...
> But just saying "maxit=100" will simply create a new variable with name
> "maxit" which you can then use in further calculations or as parameter and
> so on.

Ok, I got that from the manual and my understanding was to use it in the same 
way as basis= and geomtyp= 
Thanks to Kirk's earlier email it seems to work now.

Thanks for your suggestions!

All the best


Jörg Saßmannshausen
Research Fellow
University of Strathclyde
Department of Pure and Applied Chemistry
295 Cathedral St.
G1 1XL

email: jorg.sassmannshausen at strath.ac.uk
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