Summer School 2021 Wed.4.Ponce exercise2 Mobility

[mjankousky]

Hello all,

I would appreciate some help troubleshooting my results for one of the tutorials from the 2021 Summer School. I am unable to get EPW to return the value of mobility and hall factor listed at the end of the epw2.out file in the Summer School 2021 tutorial Wed.4.ponce/exercise2.

The note at the end of the epw2.in file states

"""
! Note: for reference, if you use ecutwfc = 100, nk1=nk2=nk3 = 10, nq1=nq2=nq3 = 5
! and nkf1=nkf2=nkf3=nqf1=nqf2=nqf3 = 60 and mob_maxiter = 300, you should get:
! SERTA mobility = 0.26719E+03 and SERTA Hall factor = 0.486742
! BTE mobility = 0.33361E+03 and BTE Hall factor = 0.602855
! and with SOC and the same parameters, you should get:
! SERTA mobility = 0.25971E+03 and SERTA Hall factor = 0.414480
! BTE mobility = 0.32871E+03 and BTE Hall factor = 0.553747
"""

My resulting SERTA and BTE mobility values without spin orbit coupling are about 15% larger than those suggested at the end of the tutorial file.

I am using QE v.6.8 with EPW v.5.4., and I am using input files identical to those in the tutorial, with the following exceptions:

scf.in: ecutwfc = 100 (I also ran these calculations with a 10x10x10 kpoint grid instead of 8x8x8 in the scf calculation, and had very similar results)

ph.in: q1=q2=q3=5

nscf.in: ecutwfc = 100, kmesh generated with $PATHQE/wannier90-3.1.0/utility/kmesh.pl 10 10 10

epw1.in: nk1=nk2=nk3=10, nq1=nq2=nq3=5

epw2.in: nk1=nk2=nk3=10, nq1=nq2=nq3=5



The relevant output from my calculation is below:

Summary and Hall factor
=============================================================================================
BTE in the self-energy relaxation time approximation (SERTA)
=============================================================================================

Temperature: 300.0000 K
Conductivity tensor without magnetic field | with magnetic field [Siemens/m]
0.49974E-01 -0.14880E-19 0.86187E-20 | 0.49974E-01 0.29493E-06 0.14782E-18
0.20131E-19 0.49974E-01 -0.20180E-19 | -0.29493E-06 0.49974E-01 -0.19657E-18
0.92731E-20 -0.32782E-19 0.49974E-01 | -0.65418E-19 -0.20791E-18 0.49974E-01
Mobility tensor without magnetic field | with magnetic field [cm^2/Vs]
0.31192E+03 -0.92875E-16 0.53795E-16 | 0.31192E+03 0.18409E-02 0.92264E-15
0.12565E-15 0.31192E+03 -0.12596E-15 | -0.18409E-02 0.31192E+03 -0.12269E-14
0.57880E-16 -0.20462E-15 0.31192E+03 | -0.40832E-15 -0.12977E-14 0.31192E+03
Hall factor
0.851302E+05 0.502418E+00 0.222446E-12
-0.502418E+00 0.851302E+05 -0.266108E-12
-0.143034E-12 -0.242490E-12 0.851302E+05

=============================================================================================
BTE
=============================================================================================

Temperature: 300.0000 K
Conductivity tensor without magnetic field | with magnetic field [Siemens/m]
0.60831E-01 -0.46161E-19 -0.24897E-18 | 0.60831E-01 0.51956E-06 0.25549E-18
0.11205E-19 0.60831E-01 -0.13009E-18 | -0.51956E-06 0.60831E-01 -0.19566E-18
0.58793E-19 -0.49440E-19 0.60831E-01 | 0.69738E-18 -0.25443E-19 0.60831E-01
Mobility tensor without magnetic field | with magnetic field [cm^2/Vs]
0.37969E+03 -0.28812E-15 -0.15540E-14 | 0.37969E+03 0.32429E-02 0.15947E-14
0.69938E-16 0.37969E+03 -0.81200E-15 | -0.32429E-02 0.37969E+03 -0.12213E-14
0.36697E-15 -0.30859E-15 0.37969E+03 | 0.43528E-14 -0.15880E-15 0.37969E+03
Hall factor
0.699354E+05 0.597316E+00 0.866173E-12
-0.597316E+00 0.699354E+05 0.741787E-13
0.666565E-12 0.844275E-13 0.699354E+05

My values for the dielectric constant and effective charges are also slightly different than those suggested in the tutorial, but the error is closer to 1%:

Dielectric constant in cartesian axis

( 4.557932198 0.000000000 -0.000000000 )
( 0.000000000 4.557932198 0.000000000 )
( -0.000000000 0.000000000 4.557932198 )

Effective charges (d Force / dE) in cartesian axis

atom 1 B
Ex ( 1.90600 0.00000 -0.00000 )
Ey ( 0.00000 1.90600 -0.00000 )
Ez ( -0.00000 -0.00000 1.90600 )
atom 2 N
Ex ( -1.91126 0.00000 0.00000 )
Ey ( 0.00000 -1.91126 -0.00000 )
Ez ( 0.00000 -0.00000 -1.91126 )

Is this error the result of the difference in version between EPW v.5.4 and the v.5.4beta that was used at the summer school, or does it suggest that there is an error in my local compilation of EPW? Did I miss a step somewhere in the changes to the input files? Or is there something else happening that I'm not thinking of?

Thank you in advance for your help!
Matthew Jankousky
PhD Student, Metallurgical and Materials Engineering Department
Colorado School of Mines