CCL:G: PES of a triatomic molecule

 Sent to CCL by: zvitnik [zvitnik()chem.bg.ac.rs]
Did you try to turn your tri-atomic molecule in four-atomic by adding one Bq atom. 
 If not, try to read: http://www.gaussian.com/g_tech/g_ur/m_molspec.htm
 Zeljko
 On 2013-11-23 23:54, mike Andaham mymagnussen],[hotmail.com wrote:
 
 Sent to CCL by: "mike  Andaham" [mymagnussen a hotmail.com]
 Hi all,
 I am quite new to Gaussian and I encountered a problem. I am trying
to run a PES of the C-C-Cl molecule. The problem is that this molecule 
 has a 2Sigma and 2PI states almost isoenergetic and, in fact, the 2PI
 splits into two components, one with a 2A' symmetry that should
 interact with the 2A' (from the 2sigma).
 I am able to obtain the two minimum (one is linear the other bent)
but when I run a PES scan (with the opt=modredundant) it stops with an 
 error when it reaches the 180 degrees (with a linear error). This is
 one of the most important parts, I wonder if there any way of doing
the PES including the 180 degrees? (so far I can do it from 120 to 178 
 degrees). I tried opt=z-matrix, opt=modredundant, sc=qf, with
 symmetry, no symmetry.... by the way, I am scanning the angle and the
 C-C bond leaving the C-Cl to optimize.
 Additionally, how can I get the correct symmetry of the PI upon
splitting? (renner-teller effect). If I could get one I think that the 
 other is simply using the guess=alter, but I can not get any symmetry
 for this state (it gives some unknown symmetry orbitals).
 Thanks,
 Mike
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