cannot reproduce the example of SiC

Post here questions linked with issue while running the EPW code

Moderator: stiwari

Post Reply
xiang xing
Posts: 2
Joined: Mon Feb 03, 2025 3:11 am
Affiliation: PhD Candidate， HKUST

cannot reproduce the example of SiC

Post by xiang xing »

Dear experts and users,

I am using EPW 5.7 with QE 7.2 to run the example of SiC. However, I cannot reproduce the same results as listed in folder of out.ref, and thus I write to you for some helps.

At first, I use the same epw.in as placed in folder sic. I get a negative DOS and further negative lambda in epw.out, shown as

Code: Select all

===================================================================
     Phonon (Imaginary) Self-Energy in the Migdal Approximation
     ===================================================================


     Fermi Surface thickness =   2.802849 eV

     Golden Rule strictly enforced with T =   0.017235 eV
     Gaussian Broadening:   0.100000 eV, ngauss=   1
     DOS = -0.000000 states/spin/eV/Unit Cell at Ef=  9.701225 eV

     ismear =     1 iq =       1 coord.:   0.00000  0.00000  0.00000 wt:   0.00013 Temp:  200.000K
     -------------------------------------------------------------------
     lambda___(   1 )=       0.000000   gamma___=       0.000000 meV   omega=      0.0000 meV
     lambda_tr(   1 )=       0.000000   gamma_tr=       0.000000 meV   omega=      0.0000 meV
     lambda___(   2 )=       0.000000   gamma___=       0.000000 meV   omega=      0.0000 meV
     lambda_tr(   2 )=       0.000000   gamma_tr=       0.000000 meV   omega=      0.0000 meV
     lambda___(   3 )=       0.000000   gamma___=       0.000000 meV   omega=      0.0000 meV
     lambda_tr(   3 )=       0.000000   gamma_tr=       0.000000 meV   omega=      0.0000 meV
     lambda___(   4 )=      -0.000000   gamma___=       0.000000 meV   omega=     95.5956 meV
     lambda_tr(   4 )=      -0.000000   gamma_tr=       0.000000 meV   omega=     95.5956 meV
     lambda___(   5 )=      -0.000000   gamma___=       0.000000 meV   omega=     95.5956 meV
     lambda_tr(   5 )=      -0.000000   gamma_tr=       0.000000 meV   omega=     95.5956 meV
     lambda___(   6 )=      -0.000000   gamma___=       0.000000 meV   omega=     95.5956 meV
     lambda_tr(   6 )=      -0.000000   gamma_tr=       0.000000 meV   omega=     95.5956 meV
     lambda___( tot )=      -0.000000
     lambda_tr( tot )=      -0.000000
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:      637 out of     1000


     ismear =     1 iq =       2 coord.:   0.00000  0.00000  0.05000 wt:   0.00013 Temp:  200.000K
     -------------------------------------------------------------------
     lambda___(   1 )=       0.010062   gamma___=      -0.000000 meV   omega=      5.5919 meV
     lambda_tr(   1 )=       0.010275   gamma_tr=      -0.000000 meV   omega=      5.5919 meV
     lambda___(   2 )=       0.004074   gamma___=      -0.000000 meV   omega=      6.0145 meV
     lambda_tr(   2 )=       0.004044   gamma_tr=      -0.000000 meV   omega=      6.0145 meV
     lambda___(   3 )=       0.007236   gamma___=      -0.000000 meV   omega=     10.3357 meV
     lambda_tr(   3 )=       0.007614   gamma_tr=      -0.000000 meV   omega=     10.3357 meV
     lambda___(   4 )=       0.000070   gamma___=      -0.000000 meV   omega=     95.5391 meV
     lambda_tr(   4 )=       0.000091   gamma_tr=      -0.000000 meV   omega=     95.5391 meV
     lambda___(   5 )=       0.000070   gamma___=      -0.000000 meV   omega=     95.5527 meV
     lambda_tr(   5 )=       0.000091   gamma_tr=      -0.000000 meV   omega=     95.5527 meV
     lambda___(   6 )=       0.000009   gamma___=      -0.000000 meV   omega=     99.0378 meV
     lambda_tr(   6 )=       0.000131   gamma_tr=      -0.000000 meV   omega=     99.0378 meV
     lambda___( tot )=       0.021519
     lambda_tr( tot )=       0.022246
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:      580 out of     1000


     ismear =     1 iq =       3 coord.:   0.00000  0.00000  0.10000 wt:   0.00013 Temp:  200.000K
     -------------------------------------------------------------------
     lambda___(   1 )=      -0.000354   gamma___=       0.000000 meV   omega=     11.3444 meV
     lambda_tr(   1 )=      -0.000371   gamma_tr=       0.000000 meV   omega=     11.3444 meV
     lambda___(   2 )=      -0.000226   gamma___=       0.000000 meV   omega=     11.6110 meV
     lambda_tr(   2 )=      -0.000252   gamma_tr=       0.000000 meV   omega=     11.6110 meV
     lambda___(   3 )=      -0.001177   gamma___=       0.000000 meV   omega=     20.6836 meV
     lambda_tr(   3 )=      -0.001191   gamma_tr=       0.000000 meV   omega=     20.6836 meV
     lambda___(   4 )=      -0.001249   gamma___=       0.000000 meV   omega=     95.3052 meV
     lambda_tr(   4 )=      -0.001251   gamma_tr=       0.000000 meV   omega=     95.3052 meV
     lambda___(   5 )=      -0.001250   gamma___=       0.000000 meV   omega=     95.3322 meV
     lambda_tr(   5 )=      -0.001250   gamma_tr=       0.000000 meV   omega=     95.3322 meV
     lambda___(   6 )=      -0.003270   gamma___=       0.000000 meV   omega=    106.5990 meV
     lambda_tr(   6 )=      -0.003270   gamma_tr=       0.000000 meV   omega=    106.5990 meV
     lambda___( tot )=      -0.007526
     lambda_tr( tot )=      -0.007586
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:      544 out of     1000


     ismear =     1 iq =       4 coord.:   0.00000  0.00000  0.15000 wt:   0.00013 Temp:  200.000K
     -------------------------------------------------------------------
     lambda___(   1 )=      -0.000001   gamma___=       0.000000 meV   omega=     16.4979 meV
     lambda_tr(   1 )=       0.000006   gamma_tr=      -0.000000 meV   omega=     16.4979 meV
     lambda___(   2 )=      -0.000000   gamma___=       0.000000 meV   omega=     16.5519 meV
     lambda_tr(   2 )=       0.000010   gamma_tr=      -0.000000 meV   omega=     16.5519 meV
     lambda___(   3 )=      -0.000347   gamma___=       0.000000 meV   omega=     30.9224 meV
     lambda_tr(   3 )=      -0.000255   gamma_tr=       0.000000 meV   omega=     30.9224 meV
     lambda___(   4 )=      -0.000150   gamma___=       0.000000 meV   omega=     94.8124 meV
     lambda_tr(   4 )=      -0.000171   gamma_tr=       0.000000 meV   omega=     94.8124 meV
     lambda___(   5 )=      -0.000150   gamma___=       0.000000 meV   omega=     94.8216 meV
     lambda_tr(   5 )=      -0.000171   gamma_tr=       0.000000 meV   omega=     94.8216 meV
     lambda___(   6 )=      -0.000499   gamma___=       0.000000 meV   omega=    113.2321 meV
     lambda_tr(   6 )=      -0.000369   gamma_tr=       0.000000 meV   omega=    113.2321 meV
     lambda___( tot )=      -0.001149
     lambda_tr( tot )=      -0.000949
     -------------------------------------------------------------------
. But in out.ref, DOS is positive and results are normal, shown as

Code: Select all

===================================================================
     Phonon (Imaginary) Self-Energy in the Migdal Approximation (on the fly)
     ===================================================================


     Fermi Surface thickness =   6.802849 eV

     Golden Rule strictly enforced with T =   0.000006 eV
     Gaussian Broadening:   1.020427 eV, ngauss=   1
     DOS =  0.052842 states/spin/eV/Unit Cell at Ef=  9.417477 eV

     ismear =     1 iq =     1 coord.:   0.00000  0.00000  0.00000 wt:   0.00013
     -------------------------------------------------------------------
     lambda(   1 )=      0.0000   gamma=      0.0000 meV   omega=     -0.0407 meV
     lambda(   2 )=      0.0000   gamma=      0.0000 meV   omega=     -0.0407 meV
     lambda(   3 )=      0.0000   gamma=      0.0000 meV   omega=     -0.0363 meV
     lambda(   4 )=      0.3027   gamma=      0.4465 meV   omega=     94.2692 meV
     lambda(   5 )=      0.3027   gamma=      0.4465 meV   omega=     94.2692 meV
     lambda(   6 )=      0.3027   gamma=      0.4465 meV   omega=     94.2692 meV
     lambda( tot )=      0.9080
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:     1000 out of     1000


     ismear =     1 iq =     2 coord.:   0.00000  0.00000  0.05000 wt:   0.00013
     -------------------------------------------------------------------
     lambda(   1 )=      0.2392   gamma=      0.0013 meV   omega=      5.7117 meV
     lambda(   2 )=      0.1503   gamma=      0.0009 meV   omega=      6.0071 meV
     lambda(   3 )=      0.2720   gamma=      0.0048 meV   omega=     10.2722 meV
     lambda(   4 )=      0.2924   gamma=      0.4324 meV   omega=     94.3840 meV
     lambda(   5 )=      0.2925   gamma=      0.4326 meV   omega=     94.3925 meV
     lambda(   6 )=      0.6527   gamma=      1.0335 meV   omega=     97.6626 meV
     lambda( tot )=      1.8991
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:     1000 out of     1000


     ismear =     1 iq =     3 coord.:   0.00000  0.00000  0.10000 wt:   0.00013
     -------------------------------------------------------------------
     lambda(   1 )=      0.1389   gamma=      0.0030 meV   omega=     11.4359 meV
     lambda(   2 )=      0.1180   gamma=      0.0026 meV   omega=     11.5979 meV
     lambda(   3 )=      0.2684   gamma=      0.0189 meV   omega=     20.5832 meV
     lambda(   4 )=      0.2604   gamma=      0.3862 meV   omega=     94.5221 meV
     lambda(   5 )=      0.2602   gamma=      0.3861 meV   omega=     94.5374 meV
     lambda(   6 )=      1.0083   gamma=      1.8502 meV   omega=    105.1354 meV
     lambda( tot )=      2.0542
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:     1000 out of     1000


     ismear =     1 iq =     4 coord.:   0.00000  0.00000  0.15000 wt:   0.00013
     -------------------------------------------------------------------
     lambda(   1 )=      0.0998   gamma=      0.0045 meV   omega=     16.5123 meV
     lambda(   2 )=      0.0983   gamma=      0.0045 meV   omega=     16.5376 meV
     lambda(   3 )=      0.2501   gamma=      0.0393 meV   omega=     30.7735 meV
     lambda(   4 )=      0.2221   gamma=      0.3282 meV   omega=     94.3407 meV
     lambda(   5 )=      0.2220   gamma=      0.3281 meV   omega=     94.3449 meV
     lambda(   6 )=      0.9074   gamma=      1.8819 meV   omega=    111.7731 meV
     lambda( tot )=      1.7997
     -------------------------------------------------------------------
.

In addition, I also modify the fsthick to 6.802849 ! eV aligned with the ref, and I get results of 0, shown as

Code: Select all

 ===================================================================
     Phonon (Imaginary) Self-Energy in the Migdal Approximation
     ===================================================================


     Fermi Surface thickness =   6.802849 eV

     Golden Rule strictly enforced with T =   0.017235 eV
     Gaussian Broadening:   1.020427 eV, ngauss=   1
     DOS = -0.000000 states/spin/eV/Unit Cell at Ef= 14.982862 eV

     ismear =     1 iq =       1 coord.:   0.00000  0.00000  0.00000 wt:   0.00013 Temp:  200.000K
     -------------------------------------------------------------------
     lambda___(   1 )=       0.000000   gamma___=       0.000000 meV   omega=      0.0000 meV
     lambda_tr(   1 )=       0.000000   gamma_tr=       0.000000 meV   omega=      0.0000 meV
     lambda___(   2 )=       0.000000   gamma___=       0.000000 meV   omega=      0.0000 meV
     lambda_tr(   2 )=       0.000000   gamma_tr=       0.000000 meV   omega=      0.0000 meV
     lambda___(   3 )=       0.000000   gamma___=       0.000000 meV   omega=      0.0000 meV
     lambda_tr(   3 )=       0.000000   gamma_tr=       0.000000 meV   omega=      0.0000 meV
     lambda___(   4 )=       0.000000   gamma___=       0.000000 meV   omega=     95.5956 meV
     lambda_tr(   4 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.5956 meV
     lambda___(   5 )=       0.000000   gamma___=       0.000000 meV   omega=     95.5956 meV
     lambda_tr(   5 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.5956 meV
     lambda___(   6 )=       0.000000   gamma___=       0.000000 meV   omega=     95.5956 meV
     lambda_tr(   6 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.5956 meV
     lambda___( tot )=       0.000000
     lambda_tr( tot )=       0.000000
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:      187 out of     1000


     ismear =     1 iq =       2 coord.:   0.00000  0.00000  0.05000 wt:   0.00013 Temp:  200.000K
     -------------------------------------------------------------------
     lambda___(   1 )=       0.000000   gamma___=       0.000000 meV   omega=      5.5919 meV
     lambda_tr(   1 )=       0.000000   gamma_tr=       0.000000 meV   omega=      5.5919 meV
     lambda___(   2 )=       0.000000   gamma___=       0.000000 meV   omega=      6.0145 meV
     lambda_tr(   2 )=       0.000000   gamma_tr=       0.000000 meV   omega=      6.0145 meV
     lambda___(   3 )=       0.000000   gamma___=       0.000000 meV   omega=     10.3357 meV
     lambda_tr(   3 )=       0.000000   gamma_tr=       0.000000 meV   omega=     10.3357 meV
     lambda___(   4 )=       0.000000   gamma___=       0.000000 meV   omega=     95.5391 meV
     lambda_tr(   4 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.5391 meV
     lambda___(   5 )=       0.000000   gamma___=       0.000000 meV   omega=     95.5527 meV
     lambda_tr(   5 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.5527 meV
     lambda___(   6 )=       0.000000   gamma___=       0.000000 meV   omega=     99.0378 meV
     lambda_tr(   6 )=       0.000000   gamma_tr=       0.000000 meV   omega=     99.0378 meV
     lambda___( tot )=       0.000000
     lambda_tr( tot )=       0.000000
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:      163 out of     1000


     ismear =     1 iq =       3 coord.:   0.00000  0.00000  0.10000 wt:   0.00013 Temp:  200.000K
     -------------------------------------------------------------------
     lambda___(   1 )=       0.000000   gamma___=       0.000000 meV   omega=     11.3444 meV
     lambda_tr(   1 )=       0.000000   gamma_tr=       0.000000 meV   omega=     11.3444 meV
     lambda___(   2 )=       0.000000   gamma___=       0.000000 meV   omega=     11.6110 meV
     lambda_tr(   2 )=       0.000000   gamma_tr=       0.000000 meV   omega=     11.6110 meV
     lambda___(   3 )=       0.000000   gamma___=       0.000000 meV   omega=     20.6836 meV
     lambda_tr(   3 )=       0.000000   gamma_tr=       0.000000 meV   omega=     20.6836 meV
     lambda___(   4 )=       0.000000   gamma___=       0.000000 meV   omega=     95.3052 meV
     lambda_tr(   4 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.3052 meV
     lambda___(   5 )=       0.000000   gamma___=       0.000000 meV   omega=     95.3322 meV
     lambda_tr(   5 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.3322 meV
     lambda___(   6 )=       0.000000   gamma___=       0.000000 meV   omega=    106.5990 meV
     lambda_tr(   6 )=       0.000000   gamma_tr=       0.000000 meV   omega=    106.5990 meV
     lambda___( tot )=       0.000000
     lambda_tr( tot )=       0.000000
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:      124 out of     1000


     ismear =     1 iq =       4 coord.:   0.00000  0.00000  0.15000 wt:   0.00013 Temp:  200.000K
     -------------------------------------------------------------------
     lambda___(   1 )=       0.000000   gamma___=       0.000000 meV   omega=     16.4979 meV
     lambda_tr(   1 )=       0.000000   gamma_tr=       0.000000 meV   omega=     16.4979 meV
     lambda___(   2 )=       0.000000   gamma___=       0.000000 meV   omega=     16.5519 meV
     lambda_tr(   2 )=       0.000000   gamma_tr=       0.000000 meV   omega=     16.5519 meV
     lambda___(   3 )=       0.000000   gamma___=       0.000000 meV   omega=     30.9224 meV
     lambda_tr(   3 )=       0.000000   gamma_tr=       0.000000 meV   omega=     30.9224 meV
     lambda___(   4 )=       0.000000   gamma___=       0.000000 meV   omega=     94.8124 meV
     lambda_tr(   4 )=       0.000000   gamma_tr=       0.000000 meV   omega=     94.8124 meV
     lambda___(   5 )=       0.000000   gamma___=       0.000000 meV   omega=     94.8216 meV
     lambda_tr(   5 )=       0.000000   gamma_tr=       0.000000 meV   omega=     94.8216 meV
     lambda___(   6 )=       0.000000   gamma___=       0.000000 meV   omega=    113.2321 meV
     lambda_tr(   6 )=       0.000000   gamma_tr=       0.000000 meV   omega=    113.2321 meV
     lambda___( tot )=       0.000000
     lambda_tr( tot )=       0.000000
     -------------------------------------------------------------------
. I do not know what results in that and what can I do to correct that.

Thank you in advance.
Top
stiwari
Posts: 55
Joined: Mon Jun 26, 2023 9:48 pm
Affiliation: UT Austin

Re: cannot reproduce the example of SiC

Post by stiwari »

Hi Xiang xing,

What I can see from the output is that the Fermi-level, Temperature, and the Fermi surface thickness are different in all three calculations.

file 1:
Fermi Surface thickness = 2.802849 eV

Golden Rule strictly enforced with T = 0.017235 eV
Gaussian Broadening: 0.100000 eV, ngauss= 1
DOS = -0.000000 states/spin/eV/Unit Cell at Ef= 9.701225 eV

file 2:
Fermi Surface thickness = 6.802849 eV

Golden Rule strictly enforced with T = 0.000006 eV
Gaussian Broadening: 1.020427 eV, ngauss= 1
DOS = 0.052842 states/spin/eV/Unit Cell at Ef= 9.417477 eV

file 3:
Fermi Surface thickness = 6.802849 eV

Golden Rule strictly enforced with T = 0.017235 eV
Gaussian Broadening: 1.020427 eV, ngauss= 1
DOS = -0.000000 states/spin/eV/Unit Cell at Ef= 14.982862 eV

Keep the parameters the same for a fair comparison.

Best,
Sabya.
Top
xiang xing
Posts: 2
Joined: Mon Feb 03, 2025 3:11 am
Affiliation: PhD Candidate， HKUST

Re: cannot reproduce the example of SiC

Post by xiang xing »

Dear Sabya,

Thank you for the reply.
I change the temperature to temps = 0.06962710872 ! K, and perform the calculation. Then I get the results, shown as

Code: Select all

     ===================================================================
     Phonon (Imaginary) Self-Energy in the Migdal Approximation
     ===================================================================


     Fermi Surface thickness =   6.802849 eV

     Golden Rule strictly enforced with T =   0.000006 eV
     Gaussian Broadening:   1.020427 eV, ngauss=   1
     DOS = -0.000000 states/spin/eV/Unit Cell at Ef= 14.982862 eV

     ismear =     1 iq =       1 coord.:   0.00000  0.00000  0.00000 wt:   0.00013 Temp:    0.070K
     -------------------------------------------------------------------
     lambda___(   1 )=       0.000000   gamma___=       0.000000 meV   omega=      0.0000 meV
     lambda_tr(   1 )=       0.000000   gamma_tr=       0.000000 meV   omega=      0.0000 meV
     lambda___(   2 )=       0.000000   gamma___=       0.000000 meV   omega=      0.0000 meV
     lambda_tr(   2 )=       0.000000   gamma_tr=       0.000000 meV   omega=      0.0000 meV
     lambda___(   3 )=       0.000000   gamma___=       0.000000 meV   omega=      0.0000 meV
     lambda_tr(   3 )=       0.000000   gamma_tr=       0.000000 meV   omega=      0.0000 meV
     lambda___(   4 )=       0.000000   gamma___=       0.000000 meV   omega=     95.5956 meV
     lambda_tr(   4 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.5956 meV
     lambda___(   5 )=       0.000000   gamma___=       0.000000 meV   omega=     95.5956 meV
     lambda_tr(   5 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.5956 meV
     lambda___(   6 )=       0.000000   gamma___=       0.000000 meV   omega=     95.5956 meV
     lambda_tr(   6 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.5956 meV
     lambda___( tot )=       0.000000
     lambda_tr( tot )=       0.000000
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:      187 out of     1000


     ismear =     1 iq =       2 coord.:   0.00000  0.00000  0.05000 wt:   0.00013 Temp:    0.070K
     -------------------------------------------------------------------
     lambda___(   1 )=       0.000000   gamma___=       0.000000 meV   omega=      5.5919 meV
     lambda_tr(   1 )=       0.000000   gamma_tr=       0.000000 meV   omega=      5.5919 meV
     lambda___(   2 )=       0.000000   gamma___=       0.000000 meV   omega=      6.0145 meV
     lambda_tr(   2 )=       0.000000   gamma_tr=       0.000000 meV   omega=      6.0145 meV
     lambda___(   3 )=       0.000000   gamma___=       0.000000 meV   omega=     10.3357 meV
     lambda_tr(   3 )=       0.000000   gamma_tr=       0.000000 meV   omega=     10.3357 meV
     lambda___(   4 )=       0.000000   gamma___=       0.000000 meV   omega=     95.5391 meV
     lambda_tr(   4 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.5391 meV
     lambda___(   5 )=       0.000000   gamma___=       0.000000 meV   omega=     95.5527 meV
     lambda_tr(   5 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.5527 meV
     lambda___(   6 )=       0.000000   gamma___=       0.000000 meV   omega=     99.0378 meV
     lambda_tr(   6 )=       0.000000   gamma_tr=       0.000000 meV   omega=     99.0378 meV
     lambda___( tot )=       0.000000
     lambda_tr( tot )=       0.000000
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:      163 out of     1000


     ismear =     1 iq =       3 coord.:   0.00000  0.00000  0.10000 wt:   0.00013 Temp:    0.070K
     -------------------------------------------------------------------
     lambda___(   1 )=       0.000000   gamma___=       0.000000 meV   omega=     11.3444 meV
     lambda_tr(   1 )=       0.000000   gamma_tr=       0.000000 meV   omega=     11.3444 meV
     lambda___(   2 )=       0.000000   gamma___=       0.000000 meV   omega=     11.6110 meV
     lambda_tr(   2 )=       0.000000   gamma_tr=       0.000000 meV   omega=     11.6110 meV
     lambda___(   3 )=       0.000000   gamma___=       0.000000 meV   omega=     20.6836 meV
     lambda_tr(   3 )=       0.000000   gamma_tr=       0.000000 meV   omega=     20.6836 meV
     lambda___(   4 )=       0.000000   gamma___=       0.000000 meV   omega=     95.3052 meV
     lambda_tr(   4 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.3052 meV
     lambda___(   5 )=       0.000000   gamma___=       0.000000 meV   omega=     95.3322 meV
     lambda_tr(   5 )=       0.000000   gamma_tr=       0.000000 meV   omega=     95.3322 meV
     lambda___(   6 )=       0.000000   gamma___=       0.000000 meV   omega=    106.5990 meV
     lambda_tr(   6 )=       0.000000   gamma_tr=       0.000000 meV   omega=    106.5990 meV
     lambda___( tot )=       0.000000
     lambda_tr( tot )=       0.000000
     -------------------------------------------------------------------


     Number of (k,k+q) pairs on the Fermi surface:      124 out of     1000


     ismear =     1 iq =       4 coord.:   0.00000  0.00000  0.15000 wt:   0.00013 Temp:    0.070K
     -------------------------------------------------------------------
     lambda___(   1 )=       0.000000   gamma___=       0.000000 meV   omega=     16.4979 meV
     lambda_tr(   1 )=       0.000000   gamma_tr=       0.000000 meV   omega=     16.4979 meV
     lambda___(   2 )=       0.000000   gamma___=       0.000000 meV   omega=     16.5519 meV
     lambda_tr(   2 )=       0.000000   gamma_tr=       0.000000 meV   omega=     16.5519 meV
     lambda___(   3 )=       0.000000   gamma___=       0.000000 meV   omega=     30.9224 meV
     lambda_tr(   3 )=       0.000000   gamma_tr=       0.000000 meV   omega=     30.9224 meV
     lambda___(   4 )=       0.000000   gamma___=       0.000000 meV   omega=     94.8124 meV
     lambda_tr(   4 )=       0.000000   gamma_tr=       0.000000 meV   omega=     94.8124 meV
     lambda___(   5 )=       0.000000   gamma___=       0.000000 meV   omega=     94.8216 meV
     lambda_tr(   5 )=       0.000000   gamma_tr=       0.000000 meV   omega=     94.8216 meV
     lambda___(   6 )=       0.000000   gamma___=       0.000000 meV   omega=    113.2321 meV
     lambda_tr(   6 )=       0.000000   gamma_tr=       0.000000 meV   omega=    113.2321 meV
     lambda___( tot )=       0.000000
     lambda_tr( tot )=       0.000000
     -------------------------------------------------------------------
.

In addition, I also notice that I perform scf using scf.in in the example folder. However, the fermi energy (10.6197 ev) is also different from that listed in the reference scf.out (9.3232 ev). In the reference example folder (sic), there is no scf.in and thus I am very confused with what result in the difference.

By the way, have you met the problem of negative dos and lambda? Could you give some suggestions?

Xiang Xing
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Nina Girotto
Posts: 2
Joined: Wed Mar 12, 2025 9:39 am
Affiliation: The Catholic University of Louvain

Re: cannot reproduce the example of SiC

Post by Nina Girotto »

Dear Xiang Xing,

Have you tried plotting your SiC band structure?
This material has a gap and the Fermi level listed in the scf output file should be placed somewhere inside the gap, and anywhere inside the gap the DOS is indeed = 0. This also then affects your lambda values because the expression contains the DOS in the denominator (see https://docs.epw-code.org/doc/Electron-phononCoupling.html).
I wouldn't worry too much if the Fermi level 9.32 or 10.6, as log as it is inside the gap. In a real calculation, I would advise on making a convergence test by trying multiple combinations of the k grid and smearing parameters.
Also, note that in your scf calculation, the Fermi level and DOS are obtained by taking into account the states on a coarse grid (8x8x8) while in the EPW calculation, if the Fermi level is not explicitly given as the input variable, it is calculated on a dense nkf grid using wannierized states.

In the last output that you show the Fermi energy is in fact larger: Ef= 14.982862 eV, however, as far as I see, in the SiC example, only 4 bands below the Fermi level are used for Wannierization, which means that all your bands are very much below the Ef= 14.982862 eV and you have no states participating in the k-summation to calculate the phonon linewidth because of the difference between the Fermi-Dirac factors (see expression 1 in https://docs.epw-code.org/doc/Electron-phononCoupling.html). This numenator is always 0 in your case if all your wannierized states are valence bands which are completely full (fnk = 1).

If you want to obtain realistic gamma values, you should carefully wannierize your bandstructure including some conduction bands and place your Ef to the desired value inside the gap. Note that also the temperature you use is probably too small and the result is harder to converge.

Note that this is only an example and it might not provide realistic and fully converged values.

Nina.
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