RIM and cutoff

[Daniele Varsano]

Dear Wissam,
I suspect that you can't use a zcut value bigger than acell_z as you do not have q-point
sampling in that direction. So discarding that situations, the results you get are not so awful,
even if not very satisfactory.

By the way, it seems to me that the implementation of the box cutoff in the code is different from that of the PRB 2006 paper.

Of course it is, while for the cylinder there is an analytic expression as shown in the prb, here for the box each component of the box cutoff is constructed
by summation over all G components and integration over the BZ (that's the reason why you need to calculate the RIM before constructing the
cutoff). As you need a sum over all the G'-vector to construct each G components of the coulomb cutoff, there is the possibility that the use of a
small plane wave cutoff can affect the quality of the results.
This shape of the cutoff has been tested for finite boxes, while it has been not, for isolating surfaces.
For your porblem, you can have a look to this paper:
Sohrab Ismail-Beigi, PRB 73,233103 (2006), here there is another receipt that should not be difficult to implement.

Cheers,
Daniele

[alsaidi]

Hi Daniele,

You answered my question which I did not ask about the second cutoff method.
I will try to implement it in Yambo. Any suggestions would be welcome.

Thanks.

[Daniele Varsano]

Hi Wissam,

starting from ./src/coulomb/cutoff_driver.F
should be quite clear how this part of the code is organized.
Next you will have to write the corresponding subroutine as the ones contained
in./src/coulomb/cutoff_sphere.F ./src/coulomb/cutoff_cylinder.F etc.
Just post any question if you have any doubt. If it works well, we will be
very happy to include it in the next release of the code.

Cheers,

Daniele

[sdwang]

Dear developers:
In my reprt file og GW calculation, there is:
[RD./SAVE//db.pp]-------------------------------------------
Brillouin Zone Q/K grids (IBZ/BZ): 32 63 32 63
RL vectors (WF): 14257
Electronic Temperature [ev]: 0.000000
PPA diel. fun. energies :Perdew & Zunger (xc)
wavefunctions :Perdew & Zunger (xc)
X matrix size : 477
X band range : 1 200
X e/h energy range [ev]:-1.000000 -1.000000
X Time ordering :c
X xc-Kernel :none
X Drude frequency : 0.000 0.000
X poles [o/o]: 100.0000
Rl vectors in the sum : 14257
[r,Vnl] included :no
Longitudinal Gauge :no
Field direction :0.1000E-4 0.000 0.000
BZ energy Random IM :no
BZ energy RIM points :0
PPA Im energy [ev]: 27.21138
I used >yambo -c -g n -p p -V 2,and used RIM and cutoff. I want to kown what does the key word in color mean?How I activite it in input file( My unitcell is 2D, if it is neccesarry).

[Daniele Varsano]

Dear Shudong,
this is not related with the RIM integral of BZ and the cutoff.
This is for integration of occupation number that is needed when dealing with metals.

Cheers,
Daniele

[sdwang]

Dear developers:
I try to use cylinder cut off in my nanowire system, but there is somenwrong in the report file like :

[xc] Functional Perdew & Zunger (xc)

S_x/V_xc [eV] @ K [13] (iku): 0.000000 0.000000 0.960000
<34|S_x|34> = NaN NaN <34|V_xc|34> = -10.63730 -.1713E-8
<35|S_x|35> = NaN NaN <35|V_xc|35> = -10.26887 -.2544E-8
<36|S_x|36> = NaN NaN <36|V_xc|36> = -10.40754 0.6519E-8
<37|S_x|37> = NaN NaN <37|V_xc|37> = -10.42301 -.8949E-9
<38|S_x|38> = NaN NaN <38|V_xc|38> = -9.164363 -.1198E-8
<39|S_x|39> = NaN NaN <39|V_xc|39> = -8.633402 -.1220E-8
<40|S_x|40> = NaN NaN <40|V_xc|40> = -8.664915 -.1673E-8
<41|S_x|41> = NaN NaN <41|V_xc|41> = -7.495319 0.4263E-8

The cutoff test report:
# X [au] Y [au] V_Dlat V_Rlat
#
-18.90350 -18.90350 0.03741 NaN
-18.90350 -17.25972 0.03907 NaN
-18.90350 -15.61593 0.04078 NaN
-18.90350 -13.97215 0.04254 NaN
-18.90350 -12.32837 0.04431 NaN
-18.90350 -10.68459 0.04605 NaN
-18.90350 -9.04080 0.04772 NaN
-18.90350 -7.39702 0.04926 NaN


my input file is

rim_cut # [R RIM CUT] Coulomb interaction
xxvxc # [R XX] Hartree-Fock Self-energy and Vxc
FFTGvecs= 99985 RL # [FFT] Plane-waves
RandQpts=1000000 # [RIM] Number of random q-points in the BZ
RandGvec=50 RL # [RIM] Coulomb interaction RS components
#QpgFull # [F RIM] Coulomb interaction: Full matrix
% Em1Anys
0.000 | 0.000 | 0.000 | # [RIM] X Y Z Static Inverse dielectric matrix
%
IDEm1Ref=0 # [RIM] Dielectric matrix reference component 1(x)/2(y)/3(z)
CUTGeo= "cylinder z" # [CUT] Coulomb Cutoff geometry: box/cylinder/sphere
% CUTBox
0.000 | 0.000 | 0.000 | # [CUT] [au] Box sides
%
CUTRadius= 20.000000 # [CUT] [au] Sphere/Cylinder radius
CUTCylLen= 0.000000 # [CUT] [au] Cylinder length
#CUTCol_test # [CUT] Perform a cutoff test in R-space
EXXRLvcs= 99985 RL # [XX] Exchange RL components
%QPkrange # [GW] QP generalized Kpoint/Band indices
13| 13| 34|41|
%
%QPerange # [GW] QP generalized Kpoint/Energy indices
1| 13| 0.0|-1.0|
%
and the principle axis is along z direction.
where is my error?
Thanks!

[Daniele Varsano]

Dear Shudong,
I can't see nothing wrong in your input, may be your are not
using a cubic cell.
What's the shape of your cell?


Daniele

[sdwang]

Thank you for your reply.
My unit cell is rectangular with a=b, and c is along periodic direction.

[Daniele Varsano]

OK, so something strange is happening,
In this moment I'm out, next week I will try to
reproduce your error and understand what's going wrong.

May be I will need to ask you your ground state input file.

Cheers,

Daniele

[sdwang]

In attachment is my input files.
Thanks!