# [Pw_forum] Wrong ELF values

Claudia Loyola claudial.81 at gmail.com
Tue Feb 15 16:42:23 CET 2011

```Hello!

yes, you are right if I define the vectors in function of "a" and I define
alat=a , but let me show you how I define the vectors in the scf input file:

&SYSTEM
ibrav = 0 ,
celldm(1) =1.0 ,
.
.
.
CELL_PARAMETERS (alat=1.0)
19.109476287  -0.014917030   0.000000953
-9.542147268  16.554932043   0.000000170
0.000000706   0.000000344  14.136501037

so in this case the vector basis are the real large in bohr, and the alat is
1.0 like celldm(1). Indeed, the value of the vectors for pp.x are in
function of alat, but my alat is 1.0, so I can write directly in bohr the
values of the planes that I take, in fact I take "two replicates" in each
direction. I think this is correct too.

Thank you very much for your comments :)

regards,
Claudia Loyola

On Tue, Feb 15, 2011 at 2:01 AM, Stefano de Gironcoli <degironc at sissa.it>wrote:

> Dear Claudia,
>    I may not remember correctly what the format adopted by pp.x to
> define planes is... but i think it is Cartesian coordinates in unit of
> alat (aka celldm(1)).
>
>    so when you write
>      e1(1) =38.218, e1(2)=0.0, e1(3) = 0.0,
>     e2(1) =0.0, e2(2)=33.108, e2(3) = 0.0,
> this means presumably 38 x 33 UNIT CELLS, sampled with 100x100 points
> (that is about 2-3 points in each unit cell). No surprise the FFT
> interpolation used gets confused.
>
> I think you should use more sensible values for e1(1) and e2(2)... what
> is your value of celldm(1)?
>
> At least this is my guess.
>
> stefano
>
>
> On 02/14/2011 06:57 PM, Claudia Loyola wrote:
> > Well, this is one of the input file:
> >
> > &inputpp
> >   &plot
> >      nfile = 1 ,
> >      filepp(1) = 'Ba38_33_10.charge' ,
> >      weight(1) = 1.0 ,
> >      iflag = 2 ,
> >      output_format = 3 ,
> >      fileout = 'ba.rho38_33_10.xsf' ,
> >      x0(1) =0.0, x0(2)=0.0, x0(3) = 10.602,
> >      e1(1) =38.218, e1(2)=0.0, e1(3) = 0.0,
> >      e2(1) =0.0, e2(2)=33.108, e2(3) = 0.0,
> >      nx=100, ny=100
> >   /
>
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--
Claudia Loyola Canales
Postdoc in Computational Physics
Iowa State University
Iowa, USA
http://www.lpmd.cl/claudial
<http://www.lpmd.cl/claudial>http://www.lpmd.cl
http://cosmic.mse.iastate.edu/
http://www.gnm.cl
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