# CCL:G: Error imposing constraints in Gaussian

*From*: "Roman D Gorbunov"
<rgorbuno:_:aecom.yu.edu>
*Subject*: CCL:G: Error imposing constraints in Gaussian
*Date*: Thu, 12 Mar 2009 10:37:15 -0400

Sent to CCL by: "Roman D Gorbunov" [rgorbuno-,-aecom.yu.edu]
Dear CCL Subscribers,
I try to run a geometry optimization in which the structure of the molecule is
restricted to be planar (this is a 2 nucleotide system, a base-pare). My
calculation crashed. In the end I have the following message:
Iteration100 RMS(Cart)= 0.00004173 RMS(Int)= 0.00140344
New curvilinear step not converged.
Error imposing constraints
Error termination via Lnk1e in /opt/g03/l103.exe at Mon Mar 9 13:29:22 2009.
Job cpu time: 0 days 6 hours 9 minutes 54.8 seconds.
File lengths (MBytes): RWF= 134 Int= 0 D2E= 0 Chk= 20 Scr=
1
I found that in the CCL list peoples already discussed this problem:
http://server.ccl.net/cgi-bin/ccl/message-new?2003+05+23+007.
However, this message does not help me. It is written there that the problem can
appear if "the fixed torsional or dihedral angles are far from that of the
starting geometry". It is not my case since I do NOT have 2 values for the
same coordinate("starting" one and "fixed" one). For every
internal coordinate I have only one value and than in the end of the input file
I specify the internal coordinates which have to be fixed.
In the cited message also written that problem can appear if "you fix
too many redundant coordinates at once causing Gaussian to have a
difficult time funneling the forces in the remaining coordinates". It
seams to be my case. I fix a lot of dihedral angles to force the structure to be
planar. So, i probably know what is the reason of the problem but I still do not
know how to solve the problem.
Can anybody help me with that?
Thank you in advance,
Roman.