FDE runs a self-consistent calculation when a
convergence criterion is fulfilled.
The convergence criterion is the change in the total dipole moment.
This is a tight convergence criterion, as
the dipole moment is highly sensitive to small changes in electron density.
The convergence parameter
for the j
-th step in the
freeze-and-thaw procedure is computed by means the following expression
|Δμji||=||μij - μij-1 i = A, B|
FDEstops when ≤0.005 a.u.. The default value for the convergence criteria can be changed using the flag
--epsilon=real where real is a decimal number.
The maximum number of freeze-and-thaw cycles can be specified by
--max-iter= integer, and the default value is 20.
In order to make easy the convergence of the iterative solution of the KSCED coupled equations, a damping factor η must be used for the matrix elements of the embedding potential vemb as perturbation to a given subsystem
|dvemb = (1 - η)vemb + ηvemb||(15.11)|
FDEthe starting value of η can be changed using
--start-damp=real (default value is 0.45 ) where real is a decimal number. The damping parameter can also dynamically change at each iterative step (according to the convergence process) of a quantity set by
--step-damp=real (default value is 0.10 ). The minimum value set by
--max-damp=real (default value is 0.90 ).