about some parameters in the New Calculator of 12.2.8

[njuxyh]

Dear all:
i have some issues unclear about the setting up in the New Calculator, so please help me ;

first if i choose the ATK-DFT option, in the basic settings, there are a box "NO SCF interation", i saw in the example http://quantumwise.com/publications/tutorials/mini-tutorials/95-optimizing-the-geometry-of-a-two-probe-system , it says click it means only relax the scatter region? the eletrode is fixed?
 
but when i do a scf calculation, and then calculate the transmission spectra, the electronic density SCF interaction is needed, why in the another example [url]]http://quantumwise.com/publications/tutorials/mini-tutorials/95-optimizing-the-geometry-of-a-two-probe-system , it says click it means only relax the scatter region? the eletrode is fixed?
 
but when i do a scf calculation, and then calculate the transmission spectra, the electronic density SCF interaction is needed, why in the another example http://http://quantumwise.com/documents/manuals/latest/VNLTutorial/index.html/chap.gnr.html , the part 3. Open the second New Calculator block, and select the Extended Hückel calculator this time.
 the NO SCF interaction is still chosed.

i saw several examples, some classic potential is used in relaxing process. so i am wondering in a serious calculation(for publication), it is OK? because i used DFT method  in 2008 version. and have no idea about the classic potential method.   

where is my wrong, please help me make these questions clearly?

[kstokbro]

For the most accurate calculation always use SCF. SCF means that you perform a self consistent calculation of the electron density, and it is not related to how the relaxation is done.

For a serious calculation you can pre-relax with a classical potential, and take the relaxed configuration of the classical potential and relax with DFT.

[njuxyh]

you said the For the most accurate calculation always use SCF. SCF means that you perform a self consistent calculation of the electron density, and it is not related to how the relaxation is done.

i have saw the words in the step 4 the example of
http://quantumwise.com/publications/tutorials/mini-tutorials/95-optimizing-the-geometry-of-a-two-probe-system[]http://quantumwise.com/publications/tutorials/mini-tutorials/95-optimizing-the-geometry-of-a-two-probe-system[[/url]
Therefore, double-click the inserted "New Calculator" block in the right-hand panel, and open the "Iteration control parameters". Here, place a tick-mark in the box "No SCF iteration". This will cause ATK to run through only the equivalent bulk calculation, but not perform a full self-consistent calculation with transport boundary conditions, for each step in the geometry optimization[/b]

so here NO SCF interation is related the relaxation,
here what is the meaning of NO SCF interation?
so i don not  understand, relaxed only the central regoion or the whole system? the eletrode can be relaxed in 12.2.8?