[Pw_forum] regarding Wannier transport code

[Stefano Baroni]

still, I would find it perfectly legitamate that people needing a  
helping hand on WanT seek it here
cheers - SB

On Jun 17, 2008, at 5:22 PM, Andrea Ferretti wrote:

>
> Dear Stefano and T. Maitra,
>
>>    I think there are WanT users (and developers) among the  
>> subscribers
>> to PWscf forum and therefore your query may get some reply.
>>    I just  wanted to  remind you  that you are asking  information
>> about a code we have no control of, so maybe there is some other more
>> effective mean to get help.
>> stefano
>>
>
> WanT is a different project wrt Q-Espresso and at the moment is not
> distributted with it, while it is tightly
> interfaced to, and it is supposed to work with, Q-E.
>
> Said that, I think that while questions about the Q-E/WanT interface  
> may
> be proper to this forum, other questions purely related to
> WanT can be probably better suited for the WanT developers (myself, or
> anybody else from the page http://www.wannier-transport.org/contacts.html 
>  )...
>
>
>>> T.Maitra at tnw.utwente.nl wrote:
>>>
>>>> 1. How does the programme 'kgrid.f90' which is supposed to  
>>>> calculate the k-points
>>>> in the full Brillouin Zone take into account the lattice  
>>>> structure? I mean, for example
>>>> the hexagonal lattice and simple cubic should have different set  
>>>> of k-points.
>
> basically kgrid.f90 generates a kpt mesh expressed in terms of the
> reciprocal lattice vectors ("crystal" units), avoiding any  
> symmetrization
> of the kpts...
>
> such procedure is needed because the usage of symmetries is not
> currently implemented in want-2.1 (released version of the code),
> while it is going on in the cvs version...
>
>>>>
>>>> 2. When I try to do a transport calculation with single k-point  
>>>> along the transport direction
>>>> the code doesn't calculate R = (0,0,1) block of the Hamiltonian  
>>>> matrix. But with more than
>>>> k-points along the transport direction it does it. Why is that so?
>>>>
>
> basically, the inequivalent R vectors (direct
> lattice vect) you can obtain are related to the monkhorst-pack grid  
> you are using..
> 1kpt -> 1 R vect  =  (0 0 0)
>
> this is because the Hamiltonian matrix elements on the localized  
> basis are
> obtained as a discrete fourier transform:
>
> H(R) = 1/Nk \sum_k H(k) e^-ikR
>
> this is why we need to setup more that one kpt in the transport
> direction...
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
[+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

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