[Pw_forum] input for resp_mat.x in to optimize the U for LDA+U calculations

[pc229 at kent.ac.uk]

Thanks a lot Matteo! 



----- Original Message -----

From: matteo at umn.edu

Date: Thursday, May 28, 2009 10:24 am

Subject: Re: [Pw_forum] input for resp_mat.x in to optimize the U for LDA+U calculations

To: PWSCF Forum <pw_forum at pwscf.org>



> 

> Dear Pieremanuele,

> 

> if you don't have the crystal coordinates of the atoms you can 

> have the 

> code print them.

> 

> 

> On May 27 2009, Pieremanuele Canepa wrote:

> 

> >Dear all,

> >I was  able to compile  the program resp_mat.f90 in 

> order to  carry out the

> >U in a self consistent way. Now I am trying to write up 

> correctly the input

> >for resp_mat.x. I have realized reading trough the guide (found 

> at link

> >http://vlab.msi.umn.edu/events/lecture.shtml)  that I do 

> need to have an

> >external file   with the fractional coordinate of the 

> atom belonging to the

> >supercell.

> >Actually, if I look at those external file (call for example 

> pos....) that

> >come togheter with the guide found online, the second part is 

> concerning to

> >the fractional coordinate of the atoms in the supercell, while 

> what is the

> > first part? Are these the vector of the supercell in Cartesian 

> > coordinates ?

> 

> yes.

> 

> >Why, when  for instance  the   Cartesian 

> coordinate of the  supercell

> >vectors printed in the early part of the PWscf output are:

> >  crystal axes: (cart. coord. in units of a_0)

> >               a(1) = (  1.000000  0.000000  0.000000 )

> >               a(2) = (  0.000000  1.000000  0.000000 )

> >               a(3) = (  0.000000  0.000000  1.000000 )

> >in the file pos  these become

> >20.d0 0.d0 0.d0

> >0.d0 20.d0 0.d0

> >0.d0 0.d0 20.d0

> >?

> 

> it doesn't matter the length of the vectors. only the ratio 

> between length 

> does.

> This is used to compute the distance between atoms ut the scale 

> doesn't 

> matter at all.

> 

> 

> >The cell parameter  in this case is 10.8400 (FeNi in the guide)

> >

> >Another question is : what does the line   back = 

> 'neutral' mean  in the

> >input file for resp_mat.x?

> >

> 

> neutral means that you are enforcing the total response of the 

> system to be 

> neutral. so there will be a compensating "background" term in 

> the response 

> matrix that results in an additional column and row. see PRB 71 35105.

> 

> hope this helps. 

> 

> regards,

> 

> Matteo

> 

> 

> I hope  you can get my point!

> >Best Regards, Piero

> >

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> 



---

Pieremanuele Canepa

Room 230

School of Physical Sciences, Ingram Building, 

University of Kent, Canterbury, Kent, 

CT2 7NH

United Kingdom




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