On calculating the DOS

[Harry K]

Hi All,

I'm a little confused about how the DOS calculation works. I assumed that task 10 is a primarily post-processing task and hence that it is relatively fast. So I've done a converged self-consistent ground state calculation, and then want to use the following input file to do a non-self-consistent calculation on a denser grid, then calculate the DOS.
The problem is that this is taking a very long time. The nscf calculation part goes fine and finishes, but it seems to get stuck on task 10 for so long that none of my calculations have even finished (even with the wplot parameters turned down so low as below). Time wise, the one below failed to finish when given 48 hrs to run and MPI parallelised over 192 cores. Sorry I can't give any more specific timing info.

Am I missing something here? Any help is appreciated.

Harry

tasks
1
10

xctype
20

dosmsum
true

mixtype
3

swidth
0.005

epsengy
0.00001

autolinengy
true

rgkmax
8

gmaxvr
12

spinorb
true

spinpol
true

maxscl
1

nempty
12

sppath
'/work/y07/y07/cse/elk/elk-4.0.15/species/'

avec
13.44410000       0.000000000       0.000000000
0.000000000       8.428400000       0.000000000
0.000000000       0.000000000       14.71210000

reducebf
0.5

atoms
3                                    : nspecies
'Pr.in'                                  : spfname
4                                    : natoms; atpos, bfcmt below
0.025400   0.250000   0.318300   0.00001   0.0   0.0
0.974600   0.750000   0.681700   0.00001   0.0   0.0
0.474600   0.750000   0.818300   0.00001   0.0   0.0
0.525400   0.250000   0.181700   0.00001   0.0   0.0
'Pt.in'                                 : spfname
4                                    : natoms; atpos, bfcmt below
0.281500   0.250000   0.612900
0.718500   0.750000   0.387100
0.218500   0.750000   0.112900
0.781500   0.250000   0.887100
'Al.in'                                 : spfname
4                                    : natoms; atpos, bfcmt below
0.147900   0.250000   0.934300
0.852100   0.750000   0.065700
0.352100   0.750000   0.434300
0.647900   0.250000   0.565700

ngridk
18 36 18

wplot
200
50
2
-0.4 0.2

[Harry K]

Does anyone have any tips on this? Perhaps I have a misunderstanding of wplot

[Muhammad Avicenna Naradipa]

Hi Harry,

wplot is dependent of the k-point. If you look at the logfile, the calculation of DOS and band structure (task 20) is only using one core. I think this is because of the huge number of k-points that you have combined with only one core to integrate all of the k-points.

I usually leave wplot to default, it should be sufficient. I tried increasing the nwplot to 1000 and my calculation also took a long time.

Best,
Cenna

[Harry K]

So is my non-self-consistent calculation necessary? Or is it sufficient to do a normal, self-consistent, converged ground state and then rely on wplot to do the finer interpolation of the Brillouin zone?

[Muhammad Avicenna Naradipa]

Dear Harry,

Depends on what you need. If you want DOS, band structure, etc. then you need the non-SC calculation.

Or is it sufficient to do a normal, self-consistent, converged ground state and then rely on wplot to do the finer interpolation of the Brillouin zone?

If you do a normal (i.e. small k-point sampling) then you'd get a normal DOS. Increaseing the parameters in wplot would just make the points smaller but I don't think this would increase the actual shape or resultion of the DOS. It would just take longer to calculate and you'd get like hundreds of points for the same data.

I think for resultion you should rely on k-point sampling AND swidth. You can read about it in previous posts in the forum.

Best,
Cenna