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Some questions about Lead example in 2018 worksop 
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Joined: Wed Jan 13, 2016 7:25 pm
Posts: 522
University: Oxford
Post Re: Some questions about Lead example in 2018 worksop
Dear Inoka,

0) The reason I said that was because in your output it was written " PWscf started at: Mon May 7 20:25:52 CST 2018
forrtl: severe (24): end-of-file during read, unit 5, file /proc/8616/fd/0"

1) Indeed those two variables have been removed as written in the log changes for the upcoming EPW 5: http://epw.org.uk/Main/About (toward the end).

2) Denationalization errors happen when your scattering rate is very small and therefore the mobility is super large. This is because you might not have enough k or q-points that contributes.
One way to fix this is to increase the restart frequency to 4000 for example. In that way, the code will only try to print the mobility after 4000 q-points.
You might need more k/q to have no zero scattering.
You can look at the values in the scattering output files.

Best wishes,
Samuel

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Dr. Samuel Poncé
Department of Materials
University of Oxford
Parks Road
Oxford OX1 3PH, UK


Thu May 17, 2018 11:19 am
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Joined: Fri May 18, 2018 1:32 am
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University: East China Normal
Post Re: Some questions about Lead example in 2018 worksop
Dear Samuel,

I got the similar result in the exercise of Wed5/exercise2/si (mobility) with QE v.6.2.2 but I still have two questions.

1) In epw1.in, can I use the denser fine k/q grids instead of setting filkf (filqf) = './LGX.txt' since the band structure is not that important.

2) In epw2.in, the fine q points grid was assumed but you still set filkf = './kpt.txt'. So similarly, can I also use the fine k points grid (for example, nkf1 = 10, nkf2 = 10, nkf3 = 10)? Actually I did this, but the result seems weird. The calculation was successfully done but the mobility was rathar large. I also checked the output file of scattering rate and most of the imaginary parts are zero.

Thank you.

Best,
Menglin


Fri May 18, 2018 2:02 am
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Post Re: Some questions about Lead example in 2018 worksop
Dear Menglin,

The epw1.in does not compute mobility. You can use any fine grid you want.

For epw2.in, you need to use very dense grids (100x100x100 or more) to converge the mobility.

Alternatively you can oversample the band edges since they will be the one that contribute to the mobility. Note that the weights needs to be correct.

Best wishes,
Samuel

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Dr. Samuel Poncé
Department of Materials
University of Oxford
Parks Road
Oxford OX1 3PH, UK


Fri May 18, 2018 4:24 pm
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Joined: Sun Oct 16, 2016 5:41 pm
Posts: 31
University: Kyushu university
Post Re: Some questions about Lead example in 2018 worksop
Dear Dr. Samuel

I wanted to see the Im/Re and to get wannier functions in the same Si example. So I added write_wfn=.true. and wdata(12) = 'wannier_plot= true' . Now the epw1.in input is as copied below. However I am getting a strange problem now, when epw1.in is running it creates only up to UNK00014.1, but it gives me an error for UNK00015.1 and the job crashes ( forrtl: severe (24): end-of-file during read, unit 11, file /home/EPW-2018-WS/exercise2/4-si/UNK00015.1)

If I am correct, according to my input I should have 100 UNK files because LGX.txt has 100 points. I am confused why this creates only 14 files?

I tried another calculation to get Im/Re and wannier functions with QE 6.2.2. But similar issue arrives. Can this be a bug in QE 6.2.2?


Thank you very much.

Inoka


--
&inputepw
prefix = 'si'
amass(1) = 28.0855
outdir = './'

elph = .true.
kmaps = .false.
epbwrite = .true.
epbread = .false.
epwwrite = .true.
epwread = .false.
etf_mem = 1

nbndsub = 8
nbndskip = 0

lifc = .true.
asr_typ = 'crystal'
write_wfn=.true.

wannierize = .true.
num_iter = 1500
iprint = 2
dis_win_max = 18
dis_froz_max= 8.5
proj(1) = 'Si : sp3'


wdata(1) = 'bands_plot = .true.'
wdata(2) = 'begin kpoint_path'
wdata(3) = 'L 0.50 0.00 0.00 G 0.00 0.00 0.00'
wdata(4) = 'G 0.00 0.00 0.00 X 0.50 0.50 0.00'
wdata(5) = 'end kpoint_path'
wdata(6) = 'bands_plot_format = gnuplot'
wdata(7) = 'guiding_centres = .true.'
wdata(8) = 'dis_num_iter = 500'
wdata(9) = 'num_print_cycles = 10'
wdata(10) = 'dis_mix_ratio = 1.0'
wdata(11) = 'use_ws_distance = T'
wdata(12) = 'wannier_plot= true'

elecselfen = .false.
phonselfen = .false.
a2f = .false.

! parallel_k = .true.
! parallel_q = .false.

fsthick = 1.2 ! eV
eptemp = 1 ! K
degaussw = 0.005 ! eV

dvscf_dir = './save'

band_plot = .true.
filkf = './LGX.txt'
filqf = './LGX.txt'

nk1 = 6
nk2 = 6
nk3 = 6
nq1 = 3
nq2 = 3
nq3 = 3
/
4 cartesian
0.000000000 0.000000000 0.000000000
-0.333333333 0.333333333 -0.333333333
0.000000000 0.666666667 0.000000000
0.666666667 -0.000000000 0.666666667


Sat May 19, 2018 10:44 pm
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Joined: Wed Jan 13, 2016 7:25 pm
Posts: 522
University: Oxford
Post Re: Some questions about Lead example in 2018 worksop
Dear Inoka,

To be honest, I never used the
write_wfn=.true. functionality of EPW. From looking at the code it seems it is only calling Wannier90 routines and could be outdated.

In any case, I would suggest you to use directly Wannier90 (without using EPW) if you want to get UNKXXX files.

Best wishes,
Samuel

_________________
Dr. Samuel Poncé
Department of Materials
University of Oxford
Parks Road
Oxford OX1 3PH, UK


Sun May 20, 2018 1:39 pm
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