# Hands on TDDFT

QE TDDFPT tutorial
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I) PREPARATION
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1) Copy the .tar file to your /scratch directory:

cd /scratch
cp $WORKSHOP/TDDFT/TDDFTtutorial.tar.gz ./ 2) Unpack the archive: tar vxfz TDDFTtutorial.tar.gz 3) Go to the QEtutorial file: cd TDDFTtutorial II) RUN GROUND STATE CALCULATION FOR BENZENE ——————————————–$WORKSHOP/espresso-5.0.2/bin/pw.x < Benzene.pw-in | tee Benzene.pw-out

III) RUN TDDFPT AND CALCULATE RECURSION COEFFICIENTS
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$WORKSHOP/espresso-5.0.2/bin/turbo_lanczos.x < Benzene.tddfpt-in | tee Benzene.tddfpt-out This job will take a lot of time (approx 20 minutes). You can stop it after some iterations. A complete output file is given: Reference/Benzene.tddfpt-out The important recursion coefficients are stored in the file out/benzene.beta_gamma_z.1 In order to go on with the tutorial, without having computed yet all the coefficients yet, please copy the sample file to this filename: cp Reference/benzene.beta_gamma_z.1 out/ IV) Compute spectra ——————–$WORKSHOP/espresso-5.0.2/bin/turbo_spectrum.x < Benzene.tddfpt_pp-in

The spectrum is given in the file benzene.plot

You find in column 2: Energy [Ry]
In column 4: Im[chi(omega)]

You can compute several spectra varying in Benzene.tddfpt_pp-in

itermax0: The number of computed coefficients read from file
benzene.beta_gamma_z.1. This number must be <= the number of
coefficients stored in the file

itermax: The number of coefficients used in the continued fraction
with terminator. From itermax0 onwards, these coefficients will be
extrapolated

terminator: use “osc” for the even/odd terminator
use “no” for not using a terminator

IV) Compute charge density response
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\$WORKSHOP/espresso-5.0.2/bin/turbo_lanczos.x < Benzene.tddfpt-in-s2