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Re^2: ROUNDOFF ERROR IN BEND message when reading a Z matrix

Reinaldo Pis Diez
reinaldo.pisdiez@gmail.com


Thanks to Alex and Jim for their help/hints. I must say that I finally rearranged the original z matrix and freeze the internal coords using ifreez within $statpt.

I'd like to mention that I couldn't use ifrzat together with dlc=.t. and auto=.t. because it is limited to 16 atoms in the current version and I have much more atoms to freeze.

Also, I was unable to combine dlc=.t. and auto=.t. with ifzmat as Jim suggested. According to the INPUT section of the manual, ifzmat must have the same format as izmat. Thus, I try something like

$zmat dlc=.t. auto=.t. ifzmat(1)=1,1,2, 1,1,3 $end

to see what happens and got the message

ERROR: UNABLE TO PROJECT DLC!

after the z matrix was automatically generated. I don't know what happens here, but it is clear that the problem is with ifzmat as if it is removed, the example runs smoothly. I guess that I'm missing something here. Can anyone provide a running example using dlc/auto/ifzmat?

Thanks in advance.

Regards,

Reinaldo

On Sat Jul 31 '10 2:02am, Jim Kress wrote
-----------------------------------------
>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.pdfhttp://classic.chem.msu.su/gran/gamess/Firefly_input_rev002.pdfhttp://classic.chem.msu.su/gran/gamess/Firefly_input_rev002.pdfhttp://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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