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Constraints are violated
Problem: constraints are violated: coordinates that
were specified as frozen turn out to change during the optimization or
coordinates that should remain the same start to differ after a few geometry
update cycles.
Possible cause: there is an internal conflict between
different demands, usually: symmetry versus constraints. The problem
arises easily when a constrained optimization is requested for a molecule
with some symmetry while the coordinates were defined with a Z-matrix
structure that does not properly reflect the symmetry. Usually the deviations
from the requested constraints are small. If they are really large, there might
be a bug and you should contact an adf
representative.
Cure: redefine the Z-matrix and/or use Cartesian
optimization (if the constraints are expressible in Cartesians).
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