OUTER_SCF

[marc]

Dear all,

I'm trying to get a better understanding of the different options that
are available in cp2k by reading some papers and also to get a more
hands-on experience with DFT-calculations I'm comparing the results of
different functionals.  To get some help I was reading the cp2k user
self-support(part 3) and there I came across the OUTER_SCF option
(FORCE_EVAL%DFT%SCF%OUTER_SCF).  So my question
is what does an outer_scf cycle do exactly?  I didn't find any
reference to the literature or something similar...  Apparently it is
important for the convergence but I don't really see how.  And what is
the relation to the 'inner scf' cycle?  There should be an important
interaction between the two because the total number of iteration
steps is the product of the maximum internal and maximum external
steps...
Maybe this explained somewhere in a paper?

Thanks in advance,

marc