C1 symmetry and minima
Daniel Kost inquired about pesky imaginary freqs in optimized structures, even
when these have C1 sym. It should perhaps be pointed out that there is no
reason why a C1 structure has to be a minimum; it could be a first-order
saddle point (a transition state), a higher-order saddle point (a mountain
top), or not even a stationary point. Obviously the optimized structures
he's gettin should be stationary points, and one imag. freq. pins them
down as transition states. (Some TS's are "trivial" in that changing
a
torsional angle is essentially all that's needed to give a minimum).
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