From owner-chemistry- at -ccl.net Fri May 14 14:28:00 2010 From: "Anthony F kwyjib09]^[gmail.com" To: CCL Subject: CCL: Freq and Stability Message-Id: <-41855-100514133403-24319-2k3YdQJGeRjduStzc+k4gQ:-:server.ccl.net> X-Original-From: "Anthony F" Date: Fri, 14 May 2010 13:34:01 -0400 Sent to CCL by: "Anthony F" [kwyjib09*_*gmail.com] Dear CCL, I've been running geometry optimizations and found stationary points. I have also been using SCF = QC (also UB3LYP/6-311+G(d,p) NOSYMM). How can I be sure that my final answer is a local minimum? When I perform a frequency job after the optimization, I sometimes obtain imaginary frequencies, suggesting an nth-order saddle point (n is the number of imaginary frequencies). Does this also have to do with the stability of my wavefunction? I have used the keyword Stable=Opt for verification. But I find that I can have both a stable wavefunction and imaginary frequencies. How do I then find true local minima? Also, is it possible to run both a STABLE and geometry OPT job with the same route? Or do I have to use the Link1 keyword? If so, is it possible to copy my checkpoint file through the route section? Thanks Anthony