EPW Forum

Posted: **Mon Feb 27, 2017 3:13 pm**

Dear all,
I am trying to calculate the electron phonon coupling for Cubic P using EPW. I have performed scf and nscf calculations using QE and wannierize calculations using EPW. The kmesh in nscf calculations is 8x8x8 and the qmesh for phonon calculations is also 8x8x8. With there parameters I can get very good band structure and phonon spectrum. And the band structure and phonon dispersion from wannier interpolation match well with those of QE. see http://pan.baidu.com/s/1kVkadeB

However, when I perform the electron phonon calculations, I find that the obtained linewidth and lambda(see files in the following) are unreasonablely large along high symmetry points, which are very difference from the results from QE(electron phonon calculations). The above calculations are perfermed with "delta-delta approximation" and with normal calculations I get negative linewidth (then I change to delta-delta, but lamda is unreasonably large ). Could you give some me some suggestions? Any suggestions will be greatly appreciated. Thanks in advance!

Best Regards!
Xianxin

PS: in the following are the gamma and lambda and all input files.

The gamma is http://pan.baidu.com/s/1geXWX27. the lambda is,

#Lambda phonon self-energy

#Modes 1 2 3
1 0.00000E+00 0.00000E+00 0.00000E+00
2 0.15672E+06 0.18942E+03 0.18968E+05
3 0.11403E+06 0.94212E+02 0.14017E+05
4 0.86272E+05 0.73754E+02 0.10823E+05
5 0.64878E+05 0.76459E+02 0.83512E+04
6 0.48263E+05 0.47958E+02 0.63981E+04
7 0.35091E+05 0.92767E+02 0.48099E+04
8 0.25113E+05 0.58070E+01 0.35456E+04
9 0.17130E+05 0.58039E+01 0.24907E+04
10 0.83341E+04 0.31684E+04 0.17161E+04
11 0.74375E+04 0.67398E+02 0.11447E+04
12 0.50688E+01 0.47434E+04 0.73714E+03
13 0.60105E+03 0.22998E+04 0.45696E+03
14 0.15443E+03 0.15387E+04 0.26942E+03
15 0.94796E+03 0.83930E+01 0.15378E+03
16 0.26829E+00 0.53648E+03 0.87408E+02
17 0.36410E+00 0.30268E+03 0.50228E+02
18 0.29772E+01 0.17933E+03 0.31039E+02
19 0.11855E+03 0.31836E+00 0.20802E+02
20 0.88135E+02 0.17260E+00 0.15691E+02
21 0.67532E+02 0.16475E+00 0.12505E+02
22 0.29416E+00 0.58025E+02 0.10703E+02
23 0.53183E+02 0.31521E+00 0.92612E+01
24 0.49679E+02 0.33533E+00 0.77237E+01
25 0.23785E+00 0.44737E+02 0.57510E+01
26 0.40327E+02 0.26074E+00 0.37087E+01
27 0.36135E+02 0.39492E+00 0.19539E+01
28 0.29089E+02 0.22299E+00 0.81501E+00
29 0.19426E+02 0.91096E+00 0.43750E+00
30 0.17198E+02 0.25368E+00 0.10459E+01
31 0.17367E+02 0.33435E+00 0.21282E+01
32 0.16526E+02 0.23365E+00 0.28368E+01
33 0.13651E+02 0.28444E+00 0.29277E+01
34 0.10837E+02 0.36371E+00 0.25382E+01
35 0.96035E+01 0.41301E+00 0.23896E+01
36 0.94630E+01 0.56763E+00 0.26398E+01
37 0.82048E+01 0.59622E+00 0.24755E+01
38 0.64077E+01 0.56477E+00 0.20270E+01
39 0.57050E+01 0.49358E+00 0.15314E+01
40 0.52350E+01 0.44849E+00 0.12891E+01
41 0.49021E+01 0.48393E+00 0.12055E+01
42 0.44850E+01 0.48501E+00 0.11747E+01
43 0.40560E+01 0.51174E+00 0.11812E+01
44 0.35661E+01 0.49101E+00 0.11823E+01
45 0.31219E+01 0.48953E+00 0.11954E+01
46 0.26967E+01 0.11835E+01 0.45615E+00
47 0.24077E+01 0.11680E+01 0.44573E+00
48 0.24121E+01 0.11146E+01 0.42670E+00
49 0.26499E+01 0.10661E+01 0.44264E+00
50 0.33435E+01 0.98430E+00 0.46981E+00
51 0.29069E+01 0.87496E+00 0.46335E+00
52 0.29802E+01 0.48256E+00 0.77304E+00
53 0.22562E+01 0.47737E+00 0.70184E+00
54 0.20330E+01 0.58096E+00 0.66548E+00
55 0.17025E+01 0.77551E+00 0.66407E+00
56 0.17050E+01 0.98148E+00 0.65569E+00
57 0.18809E+01 0.12204E+01 0.65193E+00
58 0.18357E+01 0.12520E+01 0.62808E+00
59 0.18854E+01 0.14541E+01 0.58070E+00
60 0.18720E+01 0.16014E+01 0.47725E+00
61 0.18377E+01 0.32190E+00 0.16610E+01
62 0.18354E+01 0.14367E+01 0.57843E+00
63 0.16344E+01 0.12470E+01 0.57762E+00
64 0.15378E+01 0.10344E+01 0.35984E+00
65 0.18515E+01 0.98539E+00 0.28483E+00
66 0.18978E+01 0.69454E+00 0.30868E+00
67 0.20597E+01 0.63326E+00 0.38226E+00
68 0.27135E+01 0.98816E+00 0.49788E+00
69 0.33798E+01 0.14865E+01 0.62999E+00
70 0.39107E+01 0.18897E+01 0.82498E+00
71 0.46319E+01 0.19515E+01 0.10892E+01
72 0.56222E+01 0.16550E+01 0.12829E+01
73 0.79709E+01 0.15700E+01 0.14367E+01
74 0.10431E+02 0.17588E+01 0.15259E+01
75 0.14746E+02 0.27825E+01 0.17237E+01
76 0.18650E+02 0.48059E+01 0.22535E+01
77 0.23490E+02 0.82625E+01 0.37192E+01
78 0.29601E+02 0.12722E+02 0.75254E+01
79 0.38430E+02 0.16387E+02 0.15242E+02
80 0.54949E+02 0.18574E+02 0.26890E+02
81 0.90332E+02 0.22381E+02 0.40342E+02
82 0.17167E+03 0.35160E+02 0.51937E+02
83 0.36905E+03 0.68826E+02 0.57204E+02
84 0.93838E+03 0.15175E+03 0.58239E+02
85 0.24426E+04 0.32318E+03 0.53290E+02
86 0.61921E+04 0.74239E+03 0.52742E+02
87 0.13033E+05 0.19572E+04 0.50799E+02
88 0.21290E+05 0.57682E+04 0.28992E+02
89 0.31288E+05 0.19581E+05 0.12133E+01
90 0.19542E+04 0.11902E+06 0.57620E+02
91 0.00000E+00 0.00000E+00 0.00000E+00
92 0.50555E+05 0.22376E+04 0.36145E+04
93 0.85788E+04 0.47340E+03 0.59636E+03
94 0.12255E+04 0.14708E+03 0.70882E+02
95 0.17086E+03 0.84197E+02 0.69718E+01
96 0.13471E+02 0.32864E+02 0.91809E+00
97 0.64975E+00 0.91573E+01 0.54772E+00
98 0.39678E-01 0.61572E+00 0.68650E-01
99 0.33427E+00 0.40346E-01 0.23838E-01
100 0.12515E+01 0.15037E+00 0.92384E-01
101 0.11323E+01 0.22098E+00 0.75205E-01
102 0.75406E+00 0.19446E+00 0.32115E-01
103 0.50546E+00 0.14910E+00 0.12268E-01
104 0.24306E+00 0.85077E-01 0.25313E-01
105 0.10806E+00 0.55920E-01 0.62673E-01
106 0.78614E-01 0.78616E-01 0.85572E-01
107 0.12857E+00 0.11308E+00 0.75751E-01
108 0.14870E+00 0.12727E+00 0.50826E-01
109 0.14084E+00 0.13029E+00 0.45645E-01
110 0.12959E+00 0.11831E+00 0.43825E-01
111 0.11754E+00 0.94229E-01 0.45313E-01
112 0.12082E+00 0.88153E-01 0.67711E-01
113 0.12541E+00 0.10349E+00 0.12919E+00
114 0.21924E+00 0.17468E+00 0.21775E+00
115 0.46718E+00 0.29262E+00 0.30064E+00
116 0.78497E+00 0.49887E+00 0.49770E+00
117 0.10761E+01 0.80090E+00 0.75980E+00
118 0.20267E+01 0.16358E+01 0.16071E+01
119 0.68125E+01 0.38526E+01 0.39016E+01
120 0.60638E+02 0.14771E+02 0.12601E+02
121 0.46614E+02 0.46441E+02 0.46756E+02

The input kpath is

121 crystal
0.00000000 0.00000000 0.00000000 0.00826446
0.01666667 0.00000000 0.00000000 0.00826446
0.03333333 0.00000000 0.00000000 0.00826446
0.05000000 0.00000000 0.00000000 0.00826446
0.06666667 0.00000000 0.00000000 0.00826446
0.08333333 0.00000000 0.00000000 0.00826446
0.10000000 0.00000000 0.00000000 0.00826446
0.11666667 0.00000000 0.00000000 0.00826446
0.13333333 0.00000000 0.00000000 0.00826446
0.15000000 0.00000000 0.00000000 0.00826446
0.16666667 0.00000000 0.00000000 0.00826446
0.18333333 0.00000000 0.00000000 0.00826446
0.20000000 0.00000000 0.00000000 0.00826446
0.21666667 0.00000000 0.00000000 0.00826446
0.23333333 0.00000000 0.00000000 0.00826446
0.25000000 0.00000000 0.00000000 0.00826446
0.26666667 0.00000000 0.00000000 0.00826446
0.28333333 0.00000000 0.00000000 0.00826446
0.30000000 0.00000000 0.00000000 0.00826446
0.31666667 0.00000000 0.00000000 0.00826446
0.33333333 0.00000000 0.00000000 0.00826446
0.35000000 0.00000000 0.00000000 0.00826446
0.36666667 0.00000000 0.00000000 0.00826446
0.38333333 0.00000000 0.00000000 0.00826446
0.40000000 0.00000000 0.00000000 0.00826446
0.41666667 0.00000000 0.00000000 0.00826446
0.43333333 0.00000000 0.00000000 0.00826446
0.45000000 0.00000000 0.00000000 0.00826446
0.46666667 0.00000000 0.00000000 0.00826446
0.48333333 0.00000000 0.00000000 0.00826446
0.50000000 0.00000000 0.00000000 0.00826446
0.50000000 0.01666667 0.00000000 0.00826446
0.50000000 0.03333333 0.00000000 0.00826446
0.50000000 0.05000000 0.00000000 0.00826446
0.50000000 0.06666667 0.00000000 0.00826446
0.50000000 0.08333333 0.00000000 0.00826446
0.50000000 0.10000000 0.00000000 0.00826446
0.50000000 0.11666667 0.00000000 0.00826446
0.50000000 0.13333333 0.00000000 0.00826446
0.50000000 0.15000000 0.00000000 0.00826446
0.50000000 0.16666667 0.00000000 0.00826446
0.50000000 0.18333333 0.00000000 0.00826446
0.50000000 0.20000000 0.00000000 0.00826446
0.50000000 0.21666667 0.00000000 0.00826446
0.50000000 0.23333333 0.00000000 0.00826446
0.50000000 0.25000000 0.00000000 0.00826446
0.50000000 0.26666667 0.00000000 0.00826446
0.50000000 0.28333333 0.00000000 0.00826446
0.50000000 0.30000000 0.00000000 0.00826446
0.50000000 0.31666667 0.00000000 0.00826446
0.50000000 0.33333333 0.00000000 0.00826446
0.50000000 0.35000000 0.00000000 0.00826446
0.50000000 0.36666667 0.00000000 0.00826446
0.50000000 0.38333333 0.00000000 0.00826446
0.50000000 0.40000000 0.00000000 0.00826446
0.50000000 0.41666667 0.00000000 0.00826446
0.50000000 0.43333333 0.00000000 0.00826446
0.50000000 0.45000000 0.00000000 0.00826446
0.50000000 0.46666667 0.00000000 0.00826446
0.50000000 0.48333333 0.00000000 0.00826446
0.50000000 0.50000000 0.00000000 0.00826446
0.48333333 0.48333333 0.00000000 0.00826446
0.46666667 0.46666667 0.00000000 0.00826446
0.45000000 0.45000000 0.00000000 0.00826446
0.43333333 0.43333333 0.00000000 0.00826446
0.41666667 0.41666667 0.00000000 0.00826446
0.40000000 0.40000000 0.00000000 0.00826446
0.38333333 0.38333333 0.00000000 0.00826446
0.36666667 0.36666667 0.00000000 0.00826446
0.35000000 0.35000000 0.00000000 0.00826446
0.33333333 0.33333333 0.00000000 0.00826446
0.31666667 0.31666667 0.00000000 0.00826446
0.30000000 0.30000000 0.00000000 0.00826446
0.28333333 0.28333333 0.00000000 0.00826446
0.26666667 0.26666667 0.00000000 0.00826446
0.25000000 0.25000000 0.00000000 0.00826446
0.23333333 0.23333333 0.00000000 0.00826446
0.21666667 0.21666667 0.00000000 0.00826446
0.20000000 0.20000000 0.00000000 0.00826446
0.18333333 0.18333333 0.00000000 0.00826446
0.16666667 0.16666667 0.00000000 0.00826446
0.15000000 0.15000000 0.00000000 0.00826446
0.13333333 0.13333333 0.00000000 0.00826446
0.11666667 0.11666667 0.00000000 0.00826446
0.10000000 0.10000000 0.00000000 0.00826446
0.08333333 0.08333333 0.00000000 0.00826446
0.06666667 0.06666667 0.00000000 0.00826446
0.05000000 0.05000000 0.00000000 0.00826446
0.03333333 0.03333333 0.00000000 0.00826446
0.01666667 0.01666667 0.00000000 0.00826446
0.00000000 0.00000000 0.00000000 0.00826446
0.01666667 0.01666667 0.01666667 0.00826446
0.03333333 0.03333333 0.03333333 0.00826446
0.05000000 0.05000000 0.05000000 0.00826446
0.06666667 0.06666667 0.06666667 0.00826446
0.08333333 0.08333333 0.08333333 0.00826446
0.10000000 0.10000000 0.10000000 0.00826446
0.11666667 0.11666667 0.11666667 0.00826446
0.13333333 0.13333333 0.13333333 0.00826446
0.15000000 0.15000000 0.15000000 0.00826446
0.16666667 0.16666667 0.16666667 0.00826446
0.18333333 0.18333333 0.18333333 0.00826446
0.20000000 0.20000000 0.20000000 0.00826446
0.21666667 0.21666667 0.21666667 0.00826446
0.23333333 0.23333333 0.23333333 0.00826446
0.25000000 0.25000000 0.25000000 0.00826446
0.26666667 0.26666667 0.26666667 0.00826446
0.28333333 0.28333333 0.28333333 0.00826446
0.30000000 0.30000000 0.30000000 0.00826446
0.31666667 0.31666667 0.31666667 0.00826446
0.33333333 0.33333333 0.33333333 0.00826446
0.35000000 0.35000000 0.35000000 0.00826446
0.36666667 0.36666667 0.36666667 0.00826446
0.38333333 0.38333333 0.38333333 0.00826446
0.40000000 0.40000000 0.40000000 0.00826446
0.41666667 0.41666667 0.41666667 0.00826446
0.43333333 0.43333333 0.43333333 0.00826446
0.45000000 0.45000000 0.45000000 0.00826446
0.46666667 0.46666667 0.46666667 0.00826446
0.48333333 0.48333333 0.48333333 0.00826446
0.50000000 0.50000000 0.50000000 0.00826446

The obtained wannier spreads (s,p,d 9 wannier functions) are also good although all centers are not at the position of P (0 0 0),

Running Wannier90

Wannier Function centers (cartesian, alat) and spreads (ang):

( -0.16535 -0.19598 0.15609) : 0.82459
( -0.05596 -0.20615 -0.19378) : 0.83871
( 0.19547 -0.20439 0.07135) : 0.83090
( -0.16018 0.20248 0.15160) : 0.82515
( 0.05747 0.00218 0.21537) : 1.01548
( 0.19673 -0.00560 -0.18875) : 0.90904
( -0.04902 0.20358 -0.19765) : 0.83936
( -0.22007 0.00265 -0.07859) : 0.99232
( 0.20003 0.20124 0.06549) : 0.83155

The nscf and EPW input file are: P.nscf.in

Code: Select all

&CONTROL
                       title = 'CubicP_pbe'
                 calculation = 'nscf'
                      outdir = './temp'
                  pseudo_dir = './'
                      prefix = 'CubicP_pbe'
                   verbosity = 'high'
               etot_conv_thr = 0.00001
               forc_conv_thr = 0.0001
                       nstep = 100
 /
 &SYSTEM
                       ibrav = 1
                           a = 2.32
                         nat = 1
                        ntyp = 1
                     ecutwfc = 60
                     ecutrho = 240
                     nbnd    = 16
                   occupations = "smearing"
                 smearing    = "marzari-vanderbilt"
                 degauss     = 0.03D0
!                      london = .true.
                        la2F = .true.  
! electron phonon coupling
 /
 &ELECTRONS
            electron_maxstep = 200
                    conv_thr = 1.0D-7
              diago_thr_init = 1e-4
                 startingpot = 'atomic'
                 startingwfc = 'atomic'
                 mixing_mode = 'plain'
                 mixing_beta = 0.5
                 mixing_ndim = 8
             diagonalization = 'david'
 /

ATOMIC_SPECIES
    P   30.9740009308 P.pz-n-nc.UPF 

ATOMIC_POSITIONS crystal
  P   0.0000000000000000   0.0000000000000000   0.0000000000000000


K_POINTS crystal
512
  0.00000000  0.00000000  0.00000000  0.00195312
  0.00000000  0.00000000  0.12500000  0.00195312
  0.00000000  0.00000000  0.25000000  0.00195312
  0.00000000  0.00000000  0.37500000  0.00195312
  0.00000000  0.00000000  0.50000000  0.00195312
  0.00000000  0.00000000  0.62500000  0.00195312
  0.00000000  0.00000000  0.75000000  0.00195312
  0.00000000  0.00000000  0.87500000  0.00195312
  0.00000000  0.12500000  0.00000000  0.00195312
  0.00000000  0.12500000  0.12500000  0.00195312
  0.00000000  0.12500000  0.25000000  0.00195312
  0.00000000  0.12500000  0.37500000  0.00195312
  ...........

epw.in

Code: Select all

--
&inputepw
  prefix      = 'CubicP_pbe'
  amass(1)    = 30.9740009308
  outdir      = './temp/'

  iverbosity  = 3

  elph        = .true.
  epbwrite    = .false.
  epbread     = .true.
!  epbwrite    = .true.
!  epbread     = .false.

  epwwrite    = .true.
  epwread     = .false.

  nbndsub     =  9
  nbndskip    =  0

  wannierize  = .true.
  num_iter    = 1000
  iprint      = 2
  dis_win_max = 48
  dis_win_min= -10
  dis_froz_max=20
  proj(1)     = 'P:s;p;d'   

  wdata(1) = 'bands_plot = .true.'
wdata(2)= 'begin kpoint_path'
wdata(3)= 'R 0.500000000 0.50000000 0.50000000 G 0.000000000 0.00000000 0.00000000'
wdata(4)= 'G 0.000000000 0.00000000 0.00000000 X 0.500000000 0.00000000 0.00000000'
wdata(5)= 'X 0.500000000 0.00000000 0.00000000 R 0.500000000 0.50000000 0.50000000'
wdata(6)= 'R 0.500000000 0.50000000 0.50000000 M 0.500000000 0.50000000 0.00000000'
wdata(7)= 'M 0.500000000 0.50000000 0.00000000 G 0.000000000 0.00000000 0.00000000'
wdata(8)= 'G 0.000000000 0.00000000 0.00000000 X 0.500000000 0.00000000 0.00000000'
wdata(9)= 'X 0.500000000 0.00000000 0.00000000 M 0.500000000 0.50000000 0.00000000'
wdata(10)= 'end kpoint_path'
  wdata(11) = 'bands_plot_format = gnuplot'

!  elinterp    = .true.
!  phinterp    = .true.

!  tshuffle2   = .true.
!  tphases     = .false.

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

  parallel_k  = .true.
  parallel_q  = .false.

  fsthick     = 2.0 ! eV 
  eptemp      = 300 ! K (same as PRB 76, 165108)
  degaussw    = 0.4 ! eV

  delta_approx=.true.
  dvscf_dir   = '../../ph/save'
  filukk      = './Cubic_pbe.ukk'
  filqf       = 'meshes/path.dat'
!  band_plot=.true.
  nkf1        = 32 
  nkf2        = 32
  nkf3        = 32
  
  nk1         = 8
  nk2         = 8
  nk3         = 8

  nq1         = 8
  nq2         = 8
  nq3         = 8
 /
      35 cartesian
0   0   0   0.001953125
0.125   0   0   0.01171875
0.25   0   0   0.01171875
0.375   0   0   0.01171875
0.5   0   0   0.005859375
0.125   0.125   0   0.0234375
0.25   0.125   0   0.046875
0.375   0.125   0   0.046875
0.5   0.125   0   0.0234375
0.25   0.25   0   0.0234375
0.375   0.25   0   0.046875
0.5   0.25   0   0.0234375
0.375   0.375   0   0.0234375
0.5   0.375   0   0.0234375
0.5   0.5   0   0.005859375
0.125   0.125   0.125   0.015625
0.25   0.125   0.125   0.046875
0.375   0.125   0.125   0.046875
0.5   0.125   0.125   0.0234375
0.25   0.25   0.125   0.046875
0.375   0.25   0.125   0.09375
0.5   0.25   0.125   0.046875
0.375   0.375   0.125   0.046875
0.5   0.375   0.125   0.046875
0.5   0.5   0.125   0.01171875
0.25   0.25   0.25   0.015625
0.375   0.25   0.25   0.046875
0.5   0.25   0.25   0.0234375
0.375   0.375   0.25   0.046875
0.5   0.375   0.25   0.046875
0.5   0.5   0.25   0.01171875
0.375   0.375   0.375   0.015625
0.5   0.375   0.375   0.0234375
0.5   0.5   0.375   0.01171875
0.5   0.5   0.5   0.001953125

Posted: **Mon Feb 27, 2017 3:32 pm**

Dear Xianxin,

You need to check if the electron-phonon matrix elements in the Wannier representation have an appropriate decay. More info about this can be found in J. Noffsinger et al, Comput. Phys. Comm. 181, 2140 (2010).

The smearing value you are using degaussw = 0.4 also seams a bit too large.

Best,
Roxana

Posted: **Tue Feb 28, 2017 1:31 am**

roxana wrote:Dear Xianxin,

You need to check if the electron-phonon matrix elements in the Wannier representation have an appropriate decay. More info about this can be found in J. Noffsinger et al, Comput. Phys. Comm. 181, 2140 (2010).

The smearing value you are using degaussw = 0.4 also seams a bit too large.

Best,
Roxana

Dear Roxana,
Thanks so much for your suggestions. I have plotted the decay of Hamiltonian, dynamical matrix and electron-phonon matrix elements.
I find that g(0,R_p) (electron-phonon matrix elements) decays very slowly in real space. Now I have used 8x8x8 q-points, which is already very dense. Do you have any suggestions to solve this problem? Is it possible to be related to the wannier functions(when I perform wannierize calculations, I use dis_froz_max to make the wannier band better)? In PRB B 88, 064517 (2013) (Page 2, right column), the author can obtain the good electron phonon coupling constant for P just using 8x8x8 q-point(they use their own pseudopotential). I am very curious about their tricks. Any suggestions ? Thanks very much !

The decay see http://pan.baidu.com/s/1eRQ7zRc

Best Regards!
Xianxin

Posted: **Tue Feb 28, 2017 10:05 am**

Dear Xianxin,

Slow decays usually mean that the Wannier functions you obtain are not so good.

What is the final spread you obtained?

Does the Wannier function gives you a corrected interpolated bandstructure?

Best,

Samuel

Posted: **Thu Mar 02, 2017 10:08 am**

roxana wrote:Dear Xianxin,

You need to check if the electron-phonon matrix elements in the Wannier representation have an appropriate decay. More info about this can be found in J. Noffsinger et al, Comput. Phys. Comm. 181, 2140 (2010).

The smearing value you are using degaussw = 0.4 also seams a bit too large.

Best,
Roxana

Dear Roxana,
Thanks very much for your help. I have found what is going wrong. I used wrong q-points in ewp.in (equivalent q-points but not the same as in QE) and these q-points should be the same as those in QE phonon calculations. When I use the right q-points, the decay is good and I can get reasonable result. But the obtained lambda is much smaller than that in the reference.(PRB 88, 064517 (2013) (0.61 VS 0.80) You said that degaussw = 0.4 was too large. How can I choose a suitable degaussw and degaussq? just increase the k-mesh and q-mesh then make the final lambda converge? Could give me some suggestions? Thanks in advance.

Best Regards!
Xianxin

Posted: **Thu Mar 02, 2017 10:12 am**

sponce wrote:Dear Xianxin,

Slow decays usually mean that the Wannier functions you obtain are not so good.

What is the final spread you obtained?

Does the Wannier function gives you a corrected interpolated bandstructure?

Best,

Samuel

Dear Samuel,
Thanks for your reply. I am sorry that I have made some mistakes and I have solved it. The wannier functions seem to be good and the interpolated band matches well with that of QE. The spreads are
Wannier Function centers (cartesian, alat) and spreads (ang):

( -0.16535 -0.19598 0.15609) : 0.82459
( -0.05596 -0.20615 -0.19378) : 0.83871
( 0.19547 -0.20439 0.07135) : 0.83090
( -0.16018 0.20248 0.15160) : 0.82515
( 0.05747 0.00218 0.21537) : 1.01548
( 0.19673 -0.00560 -0.18875) : 0.90904
( -0.04902 0.20358 -0.19765) : 0.83936
( -0.22007 0.00265 -0.07859) : 0.99232
( 0.20003 0.20124 0.06549) : 0.83155

Best Regards!

Xianxin

Posted: **Thu Mar 02, 2017 10:17 am**

Dear Xianxin,

Glad to hear that it now works for you !

Best,

Samuel

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unreasonably large lambda in EPW for P

unreasonably large lambda in EPW for P

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