In constrained optimizations, for internal coordinates with user-specified equilibrium values, this is the force constant (in au) used to apply an additional force to each coordinate. If the user is only concerned to satify the desired constraint, then the user need only ensure that this value is sufficiently large. Alternatively, the user may specify this value to apply a force of a particular magnitude, in which case the given equilibrium value may or may not be reached by the optimization.
- Type: double
- Default: 2.0