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How to select degaussw ?
Posted: Sun Jun 02, 2019 2:46 pm
by liu xinbao
Dear all,
I am trying to calculate the electron-phonon coupling in TiSe_2 and I got the following result.
Then I'm confused about how to select correct the smearing parameter of delta function which is controlled by the tag degaussw.
I found two similar graph in the literature
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.95.024505
I have review some discussion about this parameter, I thought that if we increase k-mesh or q-mesh, the lambda will converge to an constant.
But in my case and the PRB case, the lambda just increase when sigma close to 0 even when we increase k&q mesh.
Why we can select 15meV or 35meV as the convergence criterion value?
Hope for any discussion about this.
Bests,
Xinbao,
Re: How to select degaussw ?
Posted: Mon Jun 10, 2019 12:13 pm
by ilias-serifi
HI
i have the same problem for the electron phonon coupling for an 2D metal
i got unreasonable electron phonon coupling and eliashberg spectral function for a q and k meshes 320*200*1 and 320*200*1
i had lambda = 290
Code: Select all
&inputepw
prefix = 'xx'
amass(1) = xxxxxxxxxx
outdir = './'
iverbosity = 1
!ep_coupling = .false.
elph = .true.
kmaps = .false.
epbwrite = .true.
epbread = .false.
! etf_mem = 0
epwwrite = .true.
epwread = .false.
nbndsub = 8
nbndskip = 0
wannierize = .true.
num_iter = 150
iprint = 2
dis_win_max = 20
dis_froz_max= -1
proj(1) = 'xx:l=-3'
elecselfen = .false.
! nest_fn = .false.
phonselfen = .true.
a2f = .true.
delta_approx = .true.
! specfun_el = .true.
wmin_specfun = 0
wmax_specfun = 0.001
nw_specfun = 50
! parallel_k = .true.
! parallel_q = .false.
!wdata(9) = 'kmesh_tol=0.00001'
wdata(1) = 'bands_plot = .true.'
wdata(2) = 'begin kpoint_path'
wdata(3) = 'G 0.00 0.00 0.00 X 0.50 0.00 0.00'
wdata(4) = 'X 0.50 0.00 0.00 S 0.50 0.50 0.00'
wdata(5) = 'S 0.50 0.50 0.00 Y 0.00 0.50 0.00'
wdata(6) = 'Y 0.00 0.50 0.00 G 0.00 0.00 0.00'
wdata(7) = 'end kpoint_path'
wdata(8) = 'bands_plot_format = gnuplot'
wdata(9) = 'search_shells=40'
wdata(10) = 'dis_num_iter= 20000'
fsthick = 15 ! eV
eptemp = 0.075 ! K (same as PRB 76, 165108)
degaussw = 0.025 ! eV
degaussq = 0.5 ! meV
dvscf_dir = '../phonon/save/'
filukk = './xx.ukk'
! filkf = 'xx_band.kpt'
! filqf = 'kpath.dat'
nkf1 = 320
nkf2 = 200
nkf3 = 1
nqf1 = 320
nqf2 = 200
nqf3 = 1
nk1 = 32
nk2 = 20
nk3 = 1
nq1 = 16
nq2 = 10
nq3 = 1
/
54 cartesian
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