[Pw_forum] questions about lda+u calculation

[Gianluca Giovannetti]

Dear Ivanov,

if you have a look to the file resp_mat.f90 you can check the reason to have
atomic positions read from file.
there are needed to calculate the matrix elements of chi and chi0.

atomic positions are given in fractional coordinates (direct lattice).
what about primitive vectors?

if you are considering a FeO unit cell with 8 ions you can perturb only one
Fe site (you don`t need to look at occupancies on O sites) if  all the other
Fe are equivalent to this one.
one have to perturb once all the ions which are not equivalent.

cheers,

Gianluca

2010/2/16 Максим Иванов <maaaxim at yahoo.com>

> Dear PW-users,
> I have question about calculating the response matrice in lda+u
> calculation. At the tutorial with examples at pagehttp://media.quantum-espresso.org/santa_barbara_2009_07/index.phpis used input file to calculate the matrice. In this input file you need
> file containing the atomic positions and the vectors of the unit cell plus
> number of unit cells in each direction to construct the supercell. As I
> understand response matrice is resiprocal matrix of matrix containing
> dn/dalfa derivatives. So, why does author include atomic positions in his
> program?
> In the case when there are more than two Fe atoms in FeO unit cell (let's
> say 8) is it correct to make perturbation only for one Fe atom? Or should I
> make perturbation for 8 Fe atoms and calculate 8x8 matrix?
> Thanks in advance,
> Maxim Ivanov
>
>
>
>
>
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