Re: Computing Z2 invariant for 1D graphene nanoribbons (GNRs) by Z2FH ( No.1 ) 
 Date: 2020/12/10 17:22
 Name: Hikaru Sawahata <sawahata@cphys.s.kanazawau.ac.jp>
 Dear Yubin,
I'm Hikaru Sawahata in Kanazawa university. I checked PRL article briefly.
1. The definition of Z2 invariant in 1D system is different from 2D or 3D system. Z2 invariant in 1D system (it called "Zak phase") is obtained by carrying out 1D integration on 1D Brillouin zone, and I think it can be computed by not Z2FH but polB (you need to revise the output format). >1.Does the Z2FH suitable for computing Z2 invariants of 1D GNRs?
2. Your idea is correct, and you should specify as
scf.SpinPolarization nc
You may need to specify the option as
scf.SpinOrbit.Coupling on
because SOC is an important role in many topological phenomena.
If you want to compute antiferromagnetic system, you may need to use "spin constraint method", please see the manual. http://www.openmxsquare.org/openmx_man3.9/node113.html
>2.To avoid the error from the Z2FH I need to perform the noncollinear(spinpolarized) SCF calculation, am I correct? But for the GNRs(3/5/7armchair GNRs) in the literature there should be no spin or antiferromagnetic properties. How can I do the noncollinear(spinpolarized) SCF calculation?
Regards,
Hikaru Sawahata

Re: Computing Z2 invariant for 1D graphene nanoribbons (GNRs) by Z2FH ( No.2 ) 
 Date: 2020/12/10 20:10
 Name: Yubin Fu <yubin.fu@tudresden.de>
 Dear Hikaru,
Thank you very much for your quick reply and important suggestions.
I repeated the SCF calculation of one 7AGNR by using the noncollinear(spinpolarized) parameters (scf.SpinPolarization nc, scf.SpinOrbit.Coupling on).
After the SCF calculation finished I checked the std file and found that: Sum of MulP: up = 30.00000 down = 30.00000 total= 60.00000 ideal(neutral)= 60.00000 <DFT> Total Spin Moment (muB) = 0.000000000000
That means this GNR is defined as an antiferromagnetic GNR. Then I start the Z2FH calculation. The running is quite well. But the calculated Z2.data is: Z2 invariant:(x0,xpi,y0,ypi,z0,zpi)=(0.000000,0.000000,0.000000,0.000000,0.000000,0.000000) Z2 invariant:(nu0,nu1,nu2,nu3):(0,0,0,0)
So it means that the Z2 invariant equals to 0, is it correct? From the literature, the Z2 invariant of this GNR should be 1((Phys. Rev. Lett. 119, 076401)). I understand your meaning that the Z2 invariant of 1D GNRs cannot be calculated by Z2FH.
Regarding the polB, I have checked the description. But from the out file of example, I don't know which value can be used to define the Z2 invariant. Could you please give me some more information since I am new to this area?
Thank you very much in advance.
Best regards, Yubin

Re: Computing Z2 invariant for 1D graphene nanoribbons (GNRs) by Z2FH ( No.3 ) 
 Date: 2020/12/13 01:50
 Name: Hikaru Sawahata <sawahata@cphys.s.kanazawau.ac.jp>
 Dear Yubin,
You have to read and revise the source code polB.c directly. I think "sumpsi[0]" becomes Zak phase.
>Regarding the polB, I have checked the description. But from the out file of example, I don't know which value can be used to define the Z2 invariant. Could you please give me some more information since I am new to this area?
Regards, Hikaru Sawahata

Re: Computing Z2 invariant for 1D graphene nanoribbons (GNRs) by Z2FH ( No.4 ) 
 Date: 2021/05/23 22:04
 Name: Simba <pshubham2805@gmail.com>
 I want to use openMX for DFT calculations where I want to find Chern number using calB implemented by FUKUI, HATSUGAI and SUZUKI.
In my makefile I used
CC = mpicc fopenmp O3 FC = mpicc fopenmp O3 LIB = L/opt/local/lib lfftw3 llapack lblas lmpi lmpi_mpifh lgfortran
But after a while of compiling it showed me an error.
mpicc fopenmp O3 I./elpa2018.05.001 c ./elpa2018.05.001/elpa1_compute_real.F90 ./elpa2018.05.001/elpa1_compute_real.F90:57:6:
57  use mpi  1 Fatal Error: Cannot open module file ‘mpi.mod’ for reading at (1): No such file or directory compilation terminated. make: *** [makefile:964: elpa1_compute_real.o] Error 1
I guess it successfully not installed and when I tried for calB
make calB
it showed me an error again
mpicc fopenmp O3 I./elpa2018.05.001 calB.o read_scfout.o L/opt/local/lib lfftw3 llapack lblas lmpi lmpi_mpifh lgfortran lm o calB gcc: error: lfftw3: No such file or directory make: *** [makefile:798: calB] Error 1
Although I installed openmx using
sudo aptget install openmx
But I cannot use the utility calB.
Can someone help me out what to do? How can I make calB an executable?
Thank you!

Re: Computing Z2 invariant for 1D graphene nanoribbons (GNRs) by Z2FH ( No.5 ) 
 Date: 2021/05/23 23:31
 Name: Naoya Yamaguchi
 Dear Simba,
Your error looks to be the same as http://www.openmxsquare.org/forum/patio.cgi?mode=view&no=2692
Please try $ make clean && make calB
To solve the error of `gcc: error: lfftw3: No such file or directory`, you need to replace `lfftw3` with `lfftw3`.
Regards, Naoya Yamaguchi

Re: Computing Z2 invariant for 1D graphene nanoribbons (GNRs) by Z2FH ( No.6 ) 
 Date: 2021/05/25 16:53
 Name: Simba <pshubham2805@gmail.com>
 Dear Develepors,
I am very new to OpenMX, I want to know that, is it necessary to have Band.dispersion tag turn on with the specified kpath for the calculation of Z2 invariants and Chern number in *.dat file or else it is not necessary and the Z2FH code can directly calculate Z2 and Chern number?
Thank you

Re: Computing Z2 invariant for 1D graphene nanoribbons (GNRs) by Z2FH ( No.7 ) 
 Date: 2021/05/25 22:52
 Name: Simba <pshubham2805@gmail.com>
 Hello Team,
I want to know that are these postprocessing codes calB and Z2FH valid for 2D materials and especially ones with "inversion symmetry broken"? The paper is titled with the Bulk or 3D but inside it the process is done for 2D and then 3D.
Please someone clarify.
Sincerely
