The script `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

where

Δμ^{j}_{i} |
= | μ_{i}^{j} - μ_{i}^{j-1} i = A, B |

is the difference between the dipole moments of two consecutive steps for the

`FDE`

stops when
≤0.005 a.u..
The default value for the convergence criteria can be changed using the
flag `--epsilon=`

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
*v*_{emb} as perturbation to a given subsystem

_{d}v_{emb} = (1 - η)v_{emb} + ηv_{emb} |
(15.11) |

for the

`FDE`

the starting value of `--start-damp=`

`--step-damp=`

`--max-damp=`

`fde.input`

options:

` epsilon=`

*real*

` max-iter=`

*integer*

` start-damp=`

*real*

` max-damp=`

*real*

` step-damp=`

*real*