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Pade approximation 
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Joined: Wed Oct 03, 2018 8:26 am
Posts: 10
University: NYU Shanghai
Post Pade approximation
Dear EPW developers,
I am running a calculation of isotropic Eliashberg equation + Pade approximation (given *a2f file). The calculation of isotropic Eliashberg equation is successful but the Pade approximation crashes. The error message is:

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

Backtrace for this error:
#0 0x7f26c379726f in ???
#1 0x4dd0b8 in pade_coeff_
at /gpfsnyu/home/hc76/codes/qe/qe-6.2.1/EPW/src/pade.f90:56
#2 0x4d4824 in pade_cont_iso_iaxis_to_raxis_
at /gpfsnyu/home/hc76/codes/qe/qe-6.2.1/EPW/src/eliashberg_iso_cont_raxis.f90:191
#3 0x413651 in eliashberg_iso_iaxis_
at /gpfsnyu/home/hc76/codes/qe/qe-6.2.1/EPW/src/eliashberg_iso_iaxis.f90:93
#4 0x40bdab in eliashberg_eqs_
at /gpfsnyu/home/hc76/codes/qe/qe-6.2.1/EPW/src/eliashberg.f90:44
#5 0x405028 in epw
at /gpfsnyu/home/hc76/codes/qe/qe-6.2.1/EPW/src/epw.f90:170
#6 0x404b3c in main
at /gpfsnyu/home/hc76/codes/qe/qe-6.2.1/EPW/src/epw.f90:23

I am wondering whether this is a memory issue. I set "max_memlt = 1000.0". The input file is also attached.

--
&inputepw
prefix = 'BaTiO3',
amass(1) = 137.34
amass(2) = 47.90
amass(3) = 16.00
outdir = './'

ep_coupling = .false.
elph = .false.
kmaps = .false.
epbwrite = .false.
epbread = .true.

epwwrite = .false.
epwread = .true.

parallel_k = .true.
parallel_q = .false.

fsthick = 0.5 ! eV
eptemp = 0.075 ! K
degaussw = 0.05 ! eV

a2f = .false.

dvscf_dir = './save'

fila2f = 'BaTiO3.a2f'

ephwrite = .false.
eliashberg = .true.

laniso = .false.
liso = .true.
lreal = .false.
limag = .true.
lpade = .true.

conv_thr_iaxis = 1.0d-3

max_memlt = 1000.0

wscut = 0.525 ! eV

nstemp = 2
tempsmin = 0.005
tempsmax = 0.030

nsiter = 500

muc = 0.1

nkf1 = 20
nkf2 = 20
nkf3 = 20

nqf1 = 20
nqf2 = 20
nqf3 = 20

nk1 = 4
nk2 = 4
nk3 = 4
/
10 cartesian
0.0000000 0.0000000 0.0000000 0.0312500
0.0000000 0.0000000 0.2500000 0.1875000
0.0000000 0.0000000 -0.5000000 0.0937500
0.0000000 0.2500000 0.2500000 0.3750000
0.0000000 0.2500000 -0.5000000 0.3750000
0.0000000 -0.5000000 -0.5000000 0.0937500
0.2500000 0.2500000 0.2500000 0.2500000
0.2500000 0.2500000 -0.5000000 0.3750000
0.2500000 -0.5000000 -0.5000000 0.1875000
-0.5000000 -0.5000000 -0.5000000 0.0312500

Thank you very much.

Dr. Hanghui Chen
New York University Shanghai and New York University


Fri May 10, 2019 8:21 am
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Joined: Fri Jan 22, 2016 6:48 pm
Posts: 118
University: SUNY-Binghamton
Post Re: Pade approximation
Hi,

I am not sure if max_memlt will help in your case, since that is to estimate the memory taken by the e-ph matrix elements.

I see that your temperature is very small so I assume you have a very larger number of Matsubara frequencies. I have never used the code for temperatures below 0.5 K. Since the calculation of the isotropic gap on the imaginary axis is successful, you should plot the gap as a function of temperature and see if this makes sense.

Best,
Roxana

_________________
Roxana Margine
Assistant Professor
Department of Physics, Applied Physics and Astronomy
Binghamton University, State University of New York
PO Box 6000
Binghamton, NY 13902-6000


Sat May 11, 2019 1:24 pm
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Joined: Wed Oct 03, 2018 8:26 am
Posts: 10
University: NYU Shanghai
Post Re: Pade approximation
Dear Roxana,
I increase the lowest temperature and it works now.
Thank you very much for your help. I greatly appreciate that.

Dr. Hanghui Chen
New York University Shanghai and New York University


Sun May 12, 2019 3:16 pm
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