I have been using both Gaussian09 and Gaussian16 recently to optimize some metal complexes. The Gaussian manual (for both versions) indicates that the maximum number of steps in a geometry optimization can be set by the keyword
opt. However, for every optimization I have done, Gaussian seems to consistently ignore the value set by
maxcycles and sets its own max. number of steps internally.
Most of the calculations I did have this route line:
# opt=maxcycles=200 freq b3lyp/sdd geom=connectivity
What I have noticed is that when I am minimizing the geometry, Gaussian sets maximum number of steps to
100 (with the
maxcycles=200, or to
50 if the maxcycles keyword is omitted. For transition state optimizations, the max. number of steps is set to
I have seen some discussions regarding this in various forums and mailing lists, but I have found no solution. I have also seen some posts claiming it is a bug, but it keeps happening in Gaussian16 too.
So, my question is— why does Gaussian ignore the
maxcycles keyword and how can I fix it?