[Pw_forum] How to understand Local DOS of a certain atom in qe example

[Guido Fratesi]

Dear 朱林光,

volumes are defined as boxes with edges parallel to the unit cell, 
containing the points of the (charge density) FFT grid included within 
irmin and irmax, in the three dimensions: from irmin(j,n) to irmax(j,n) 
for j=1,2,3 (n=1,n_proj_boxes). Let me try to be specific with that example:


 From the output of pw.x:

      lattice parameter (alat)  =       7.4246  a.u.

      crystal axes: (cart. coord. in units of alat)
                a(1) = (   1.000000   0.000000   0.000000 )
                a(2) = (   0.000000   1.414214   0.000000 )
                a(3) = (   0.000000   0.000000   6.000000 )

      Dense  grid:    24607 G-vectors     FFT dimensions: (  18, 25, 108)


Positions in the real-space unit cell can be measured in units of alat, 
or of bohr, or of ..., or of points along the axes as is done here: For 
example, irmin(3,1)=63 and irmax(3,1)=65 means that the first box, along 
the z-axis, extends from the 63th point to the 65th of the real-space 
mesh, out of 108 FFT points total.

The spacing between points along the z-coordinate (a(3) axis) is 
(6.000000*7.4246  a.u.)/108.

Similarly for x,y coordinates specified by irmin/max(1,*), and 
irmin/max(2,*) with 18 and 25 mesh points, respectively.

Hope this helps,

Guido





On 13/02/2017 15:04, 朱林光 wrote:
> Dear all qe users:
>     I  have  a problem of understanding Local DOS of a certain atom in qe example,especially the term irmin(*,*) and irmax in the following input file,I don't understand why and how we can do the LDOS calculations of a certain atom only by defining the value of irmin and irmax?especially how can we use the value of irmin to specify the LDOS we are going to calculate is above the surface Al not above the surface As? for example  irmin(1,1)= 0, irmax(1,1)= 2, irmin(2,1)= 0, irmax(2,1)= 2, irmin(3,1)=63, irmax(3,1)=65,
>   &projwfc
>      prefix  = 'AlAs110'
>      outdir='$TMP_DIR/',
>      ngauss=0
>      degauss=0.01
>      DeltaE=0.02
>      tdosinboxes=.true.
>      plotboxes=.true.
>      n_proj_boxes=8
>
> !! Boxes centered on the first vacuum layer:
>    !! 1) above the surface Al
>      irmin(1,1)= 0, irmax(1,1)= 2, irmin(2,1)= 0, irmax(2,1)= 2, irmin(3,1)=63, irmax(3,1)=65,
>    !! 2) above the surface As
>      irmin(1,2)= 9, irmax(1,2)=11, irmin(2,2)= 5, irmax(2,2)= 7, irmin(3,2)=63, irmax(3,2)=65,
>    !! 3) above the 2nd layer Al
>      irmin(1,3)= 9, irmax(1,3)=11, irmin(2,3)=14, irmax(2,3)=16, irmin(3,3)=63, irmax(3,3)=65,
>    !! 4) as large as the surface unit cell
>      irmin(1,4)= 1, irmax(1,4)=18, irmin(2,4)= 1, irmax(2,4)=27, irmin(3,4)=63, irmax(3,4)=65,
>
> !! Same as above, centered on the second vacuum layer:
>      irmin(1,5)= 0, irmax(1,5)= 2, irmin(2,5)= 0, irmax(2,5)= 2, irmin(3,5)=72, irmax(3,5)=74,
>      irmin(1,6)= 9, irmax(1,6)=11, irmin(2,6)= 5, irmax(2,6)= 7, irmin(3,6)=72, irmax(3,6)=74,
>      irmin(1,7)= 9, irmax(1,7)=11, irmin(2,7)=14, irmax(2,7)=16, irmin(3,7)=72, irmax(3,7)=74,
>      irmin(1,8)= 1, irmax(1,8)=18, irmin(2,8)= 1, irmax(2,8)=27, irmin(3,8)=72, irmax(3,8)=74,
>   /
>

-- 
Guido Fratesi

Dipartimento di Fisica
Universita` degli Studi di Milano
Via Celoria 16, 20133 Milano, Italy