CCL: Doubt on Optmization Output

 Sent to CCL by: Brian Salter-Duke [b_duke#,#bigpond.net.au]
 On Sat, May 28, 2011 at 05:10:43PM -0400, Guilherme Luis Cordeiro
 guilhermecord%%gmail.com wrote:
 >
 > Sent to CCL by: "Guilherme Luis  Cordeiro"
 [guilhermecord~!~gmail.com]
 > Dears members,
 >
 > I started performing an optmization on a flavonoid system containing around
 30 atoms surrounded by 3 ethanol molecules. First calculation began with AM1
 method, then I used this as a starting point for a new minimization with
 B3LYP/3-21G model chemistry. The job finished like this:
 >
 >          Item               Value     Threshold  Converged?
 >  Maximum Force            0.000004     0.000450     YES
 >  RMS     Force            0.000001     0.000300     YES
 >  Maximum Displacement     0.041333     0.001800     NO
 >  RMS     Displacement     0.006043     0.001200     NO
 >  Predicted change in Energy=-2.049104D-07
 >  Optimization completed on the basis of negligible forces.
 >     -- Stationary point found.
 > The geometry obtained, then, is being used on another minimization
 > with B3LYP/6-31G. Should restart it all over? What does mean the
 > "negligible forces" term?
 What it says. Look at the Maximum Force and RMS Force values. They are
 very small. The surface is very flat so the forces are small and the
 predicted displacements for the next step are large and never going to
 get small, so it stops. You can try restarting with a different basis
 set. It might work.
 Brian.
 > Thanks in advance.
 >
 > Guilherme Cordeiro.>
 --
                 Brian Salter-Duke (Brian Duke)
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