## Problem in real time simulation for non-linear response using yambo_nl

Questions and doubts about features of non linear optic in Yambo (yamb_nl)

Moderators: Davide Sangalli, claudio, myrta gruning

Bramhachari Khamari
Posts: 95
Joined: Wed Oct 23, 2019 5:52 am

### Problem in real time simulation for non-linear response using yambo_nl

Dear Developers,
I am facing a problem while doing the calculation for the non-linear response (Berry phase approach) for hBN. I am getting NAN value for the polarisation for the real time simulation.

* * * Polarization * * *
==========================
Volume : 385.50331780 bohr^3
Direction: 1
Numer of k-points per string : 14
Numer of different strings : 14
Electronic Phase : NaN mod(2)
Ionic Phase : -0.33333333 mod(1)
Total Phase : NaN mod(1)
Polarization : NaN mod( 4.71773722) (e/Volume).bohr
Polarization : NaN mod( 0.01223786) e/bohr^2
Polarization : NaN mod( 0.70018647) C/m^2

Direction: 2
Numer of k-points per string : 14
Numer of different strings : 14
Electronic Phase : NaN mod(2)
Ionic Phase : 0.33333333 mod(1)
Total Phase : NaN mod(1)
Polarization : NaN mod( 4.71773722) (e/Volume).bohr
Polarization : NaN mod( 0.01223786) e/bohr^2
Polarization : NaN mod( 0.70018647) C/m^2

The total polarization has module 1 !!

* * * Non-linear dynamics parameters * * *
============================================
Initial Polarization : NaN NaN NaN

Input for the calculation is given below

nloptics # [R NL] Non-linear optics
% NLBands
3 | 6 | # [NL] Bands
%
NLverbosity= "low" # [NL] Verbosity level (low | high)
NLstep= 0.0100 fs # [NL] Real Time step length
NLtime=-1.000000 fs # [NL] Simulation Time
NLintegrator= "INVINT" # [NL] Integrator ("EULEREXP/RK2/RK4/RK2EXP/HEUN/INVINT/CRANKNIC")
NLCorrelation= "SEX" # [NL] Correlation ("IPA/HARTREE/TDDFT/LRC/LRW/JGM/SEX")
NLLrcAlpha= 0.000000 # [NL] Long Range Correction
% NLEnRange
0.200000 | 8.000000 | eV # [NL] Energy range
%
NLEnSteps= 40 # [NL] Energy steps
NLDamping= 0.200000 eV # [NL] Damping
#UseDipoles # [NL] Use Covariant Dipoles (just for test purpose)
#FrSndOrd # [NL] Force second order in Covariant Dipoles
#EvalCurrent # [NL] Evaluate the current
#InducedField # [RT] Include induced field in coupling and current
NLGvecs= 4015 RL # [NL] Number of G vectors in NL dynamics for Hartree/TDDFT
% ExtF_Dir
1.000000 | 1.000000 | 0.000000 | # [NL ExtF] Versor
%
ExtF_FrStep= 0.000000 eV # [NL ExtF] Frequency step
ExtF_Int= 1000. kWLm2 # [NL ExtF] Intensity
ExtF_Width= 0.000000 fs # [NL ExtF] Field Width
ExtF_kind= "SOFTSIN" # [NL ExtF] Kind(SIN|SOFTSIN|RES|ANTIRES|GAUSS|DELTA|QSSIN)
ExtF_Tstart= 0.0100 fs # [NL ExtF] Initial Time
GfnQPdb= "E < SAVE/ndb.QP" # [EXTQP G] Database

I could not find out the reason of getting the value of polarisation as NAN. I need help to rectify this. Any suggestion will be apprecitated.

Bets wishes,
Bramhachari Khamari
Bramhachari Khamari
Post Doctoral Fellow
Department of Physics
IIT Kanpur, India.

claudio
Posts: 376
Joined: Tue Mar 31, 2009 11:33 pm
Contact:

### Re: Problem in real time simulation for non-linear response using yambo_nl

Which version of Yambo are you using?

I think this problem was solved in 4.5.1

https://github.com/yambo-code/yambo/wik ... -format%29

best
Claudio
Claudio Attaccalite
[CNRS/ Aix-Marseille Université/ CINaM laborarory / TSN department
Campus de Luminy – Case 913
13288 MARSEILLE Cedex 09
web site: http://www.attaccalite.com

Bramhachari Khamari
Posts: 95
Joined: Wed Oct 23, 2019 5:52 am

### Re: Problem in real time simulation for non-linear response using yambo_nl

Dear Sir,
Thank you for the quick reply. Right now, I am using Yambo-4.4.0. I will install newly released version that you have mentioned.

Regards,
Bramhachari Khamari
Bramhachari Khamari
Post Doctoral Fellow
Department of Physics
IIT Kanpur, India.