It is optionally possible to use the SLAPAF program written by Roland Lindh
for geometry optimizations. This is done by prepending the optimization method with 'SL'.
The following methods are supported:
- Use the rational function approximation;
- Use the Newton-Raphson method;
- Use the C1-DIIS method;
- Use the C2-DIIS method.
When using DIIS methods (SLC1 or SLC2), the DIIS parameters are specified in the same way
as in standard molpro optimizer.
There are some differences when using the SLAPAF program:
- It is not possible to use Z-matrix coordinates in the optimization.
- Instead, one can explicitly define internal coordinates to be varied or fixed.
- Additional constraints can be imposed on the converged geometry in a flexible way.