Hall mobility calculation of c-BN as mentioned in EPW 2021 tutorial

[souravrudra]

Hello developers,

I am trying to follow the hole mobility calculation of C-BN as mentioned in the EPW 2021 school in Tutorial Wed.4. I followed the following parameters as given in that pdf " 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 " . I executed the calculation using both EPW version 5.5 and 5.4.1. hall mobility results are not matching for two version, difference is quite large. I have attached here the results form two different versions.

########### Results of EPW_V_5.5##################

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

Temperature: 300.0000 K
Conductivity tensor without magnetic field | with magnetic field [Siemens/m]
0.60831E-01 -0.67875E-19 -0.33079E-19 | 0.41971E-10 0.51956E-06 -0.36942E-19
0.66254E-19 0.60831E-01 -0.11330E-19 | -0.51956E-06 0.41971E-10 -0.14605E-18
0.95649E-19 0.13877E-19 0.60831E-01 | -0.36961E-18 -0.17379E-18 0.47085E-10
Mobility tensor without magnetic field | with magnetic field [cm^2/Vs]
0.37969E+03 -0.42366E-15 -0.20647E-15 | 0.26197E-06 0.32429E-02 -0.23058E-15
0.41354E-15 0.37969E+03 -0.70715E-16 | -0.32429E-02 0.26197E-06 -0.91158E-15
0.59701E-15 0.86617E-16 0.37969E+03 | -0.23070E-14 -0.10847E-14 0.29389E-06
Hall factor
0.482531E-04 0.597317E+00 -0.424715E-13
-0.597317E+00 0.482531E-04 -0.167907E-12
-0.424924E-12 -0.199797E-12 0.541323E-04
###################################################

For EPW_V_5.5 mobility tensor with magnetic field is too low that should not be.

############### Results of EPW_V_5.4.1############################

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

Temperature: 300.0000 K
Conductivity tensor without magnetic field | with magnetic field [Siemens/m]
0.60831E-01 0.17259E-19 0.22736E-19 | 0.60831E-01 0.51956E-06 -0.25427E-18
0.40990E-19 0.60831E-01 0.53045E-19 | -0.51956E-06 0.60831E-01 0.78369E-19
0.57024E-19 -0.73230E-21 0.60831E-01 | -0.37614E-18 0.22166E-18 0.60831E-01
Mobility tensor without magnetic field | with magnetic field [cm^2/Vs]
0.37969E+03 0.10773E-15 0.14191E-15 | 0.37969E+03 0.32430E-02 -0.15871E-14
0.25585E-15 0.37969E+03 0.33109E-15 | -0.32430E-02 0.37969E+03 0.48916E-15
0.35593E-15 -0.45708E-17 0.37969E+03 | -0.23477E-14 0.13835E-14 0.37969E+03
Hall factor
0.699351E+05 0.597318E+00 -0.344605E-12
-0.597318E+00 0.699351E+05 -0.318696E-13
-0.563542E-12 0.256517E-12 0.699351E+05
#############################################################

For EPW_V_5.4.1 diagonal component of mobility values are same for both with and without magnetic field case. But I saw for BN hall and drift mobility values are different. I am not understand why such thing occurs. Also Hall factor comes out to be a tensor. So which value can be considered as hall factor as mentioned in the pdf "BTE Hall factor = 0.602855" . I have attached input output files here.

Please help me to clear my doubts.

Thanking you with regards
Sourav Rudra
PhD student
JNCASR Bengaluru India