$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:
for more info.
On Mon Jul 26 '10 0:24am, Reinaldo Pis Diez wrote
>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.