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Re: ROUNDOFF ERROR IN BEND message when reading a Z matrix

Jim Kress
jimkress_35@kressworks.com


Why don't you just use

$ZMAT DLC=.true. AUTO=.true.  $END

to automatically generate your internal coordinates.  It's much more efficient and effective.  Then, if you want to freeze any of these internal coordinates, you can use the IFZMAT/FVALUE keywords in $ZMAT.

See page 32 (and following) in this documentation:

http://classic.chem.msu.su/gran/gamess/Firefly_input_rev002.pdf

for more info.

Jim

On Mon Jul 26 '10 0:24am, Reinaldo Pis Diez wrote
-------------------------------------------------
>Dear folks,

>I'm using Firefly 7.1.G, build number 5618, to study a system containing about a hundred atoms. I'm using cartesian coordinates due to construction issues. Scf is ok, slow but convergent. Now, I have to optimize the neighborhood of a given atom, so I decide to use nzvar=3M-6 in $contrl, and "build" the z matrix in $zmat using zmat(1)=1,1,2, etc, etc. I've checked the z matrix and is ok with respect to connectivity issues.
>Despite the ifreez option I'm using to freeze almost all the internal coordinates, Firefly returns an error message during the reading of the z matrix in check mode:

>   --- ENCODED Z MATRIX ---
> COORD    TYPE     I    J    K    L    M    N
>     1       1     2    1
>     2       1     3    1
>...
>   309       3   105   69   33   21
> ROUNDOFF ERROR IN BEND - STOP

>where the 309th coord is the last one. What is the source of that error? (Almost) linear bond or torsion angles perhaps?
>I could provide the entire input if needed.
>Thanks in advance.
>Regards,

>Reinaldo  
>    


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