[Pw_forum] hubbard potential

[Matteo Cococcioni]

Dear Mojtaba,

I wil try to answer your questions one by one.

On Fri, Jan 27, 2012 at 2:50 PM, Mojtaba Rahimi <mrahimi93 at gmail.com> wrote:
> Dear all
>
> I'm using QE to calculate U-hubbard for graphene. I've used 18 atom super
> cell which has hexagonal structure, and linear response approach code, which
> is written by Dr. cococcioni. I've modified cococcioni's shell scripts which
> has been located at training part of QE website for graphene, but I've
> confronted to some problem and I have some question about this cod as well.
> I hope someone could answer me.
>
> Thanks in advance
>
> I prefer to propose my question at first:
>
> As you know in graphene pz orbital which is perpendicular to graphene plane,
> and play the most important role in transport and optical properties, isn't
> localized, but that cod is written for localized orbital such as d, and f(at
> least from my knowledge). can I use this cod for graphene?

in principle yes. I'm not sure why you want to compute the U for
graphene. have you tried to
see if U has any effect on the actual calculation?

>
> At atomic position file, the three first line specifies the parameter cell.
> Is it important that parameter cell to be cubic or it doesn't matter what it
> is?
>

in principle it is not necessary the cell to be cubic. it should work
with any cell.

> In this approach we can just determine the on-site hubbard potential. f I
> tended to determine the nearest neighbor and next nearest neighbor hubbard
> potential, how would I do them by this code?
>

if you mean intersite interactions those come for free from the
off-diagonal elements of the interaction matrix
(of which U is the diagonal).

> And my problems are:
>
> when I calculated the U for super cell dimension n=1-2, I obtained a
> negative U, which i think is wrong because U have to be positive.
>

yes it should not be the case. but I am not able to tell you what the
problem is.

> When I changed the super cell dimension to n=3,... I encountered to a
> problem which I mentioned below. How can I over com to this problem. I would
> be grateful if somebody could help me.
>

seems like a problem of memory. probably you should increase the size
of some arrays. this is my guess.

hope this helps.

Matteo



> *** glibc detected *** ./r.x: free(): invalid next size (normal): 0x09d29018
> ***
>
> ======= Backtrace: =========
>
> [0x82507db]
>
> [0x825368b]
>
> [0x81f4324]
>
> [0x81f4299]
>
> [0x805181d]
>
> [0x804824a]
>
> [0x823805d]
>
> [0x8048131]
>
> ======= Memory map: ========
>
> 08048000-082c3000 r-xp 00000000 08:11 77561870
> /home/nano2/mojtaba-work/plan/isolated-graphen/U-graphene/Ucalc/r.x
>
> 082c3000-082ce000 rwxp 0027b000 08:11 77561870
> /home/nano2/mojtaba-work/plan/isolated-graphen/U-graphene/Ucalc/r.x
>
> 082ce000-088de000 rwxp 082ce000 00:00 0
>
> 09d23000-09d45000 rwxp 09d23000 00:00 0
>
> 55555000-556d2000 rwxp 55555000 00:00 0
>
> 55700000-55721000 rwxp 55700000 00:00 0
>
> 55721000-55800000 ---p 55721000 00:00 0
>
> ffc05000-ffc2a000 rwxp 7ffffffd9000 00:00 0 [stack]
>
> ffffe000-fffff000 r-xp ffffe000 00:00 0
>
> forrtl: error (76): IOT trap signal
>
>
>
> --
> -----
> Mojtaba Rahimi (Mr.)
> Master of science -condensed matter,
>
> Email: mrahimi93 at gmail.com
>
> Phone:+ 98-9134515197
>
>
>
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>



-- 
Matteo Cococcioni
Department of Chemical Engineering and Materials Science,
University of Minnesota
421 Washington Av. SE
Minneapolis, MN 55455
Tel. +1 612 624 9056    Fax +1 612 626 7246