Geometry Optimizations in ADF is based on a quasi Newton approach [6-8], using the Hessian for computing changes in the geometry so as to make the gradients vanish. The Hessian itself is initialized (for instance based on a force field) and updated in the process of optimization.
Several subkeys in the geometry block can be used for control of the Geometry Optimization procedure and related strategy parameters.
GEOMETRY
Optim {Delocal/ Cartesian / Internal } {All / Selected}
Branch {New / Old}
Iterations Niter {Niter2}
Hessupd HessUpdate
Converge {E=TolE} {Grad=tolG} {Rad=TolR} {Angle=tolA}
Step {Rad=MaxRadStep} {Angle=MaxAngleStep} {TrustRadius=MaxRadius}
DIIS {N=NVect} {CYC=Ncyc}
Externprogram externprog.exe coord=coords.inp energy=energy.out grad=grads.out
Inithess inithessian.file
End
Optim
