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Hallo,
I have taken a small molecule 2-styryl-pyridine from literature and tried to calculate its absorption spectra with vasp to compare the results to that with TDDFT.
I have used the following input file:
Optimisation:

PREC = Normal
IBRION = 2
ENCUT = 400
NSW = 200
EDIFF = 1.0e-06
EDIFFG = -0.02
ALGO = Normal (blocked Davidson)
ISPIN = 1
INIWAV = 1
ISTART = 0
ICHARG = 2
ISMEAR = 0
SIGMA = 0.05
NPAR = 8
LREAL = AUTO

Use of LOPTICS and LCHARGE tag:
Then I copied the CONTCAR as POSCAR and run the follwing job:

PREC = Normal
IBRION = -1
ENCUT = 400
NSW = 200
EDIFF = 1.0e-06
ALGO = Normal (blocked Davidson)
ISPIN = 1
INIWAV = 1
ISTART = 0
ICHARG = 2
ISMEAR = 0
SIGMA = 0.05
NPAR = 8
LREAL = AUTO
LCHARGE=.TRUE.
LOPTICS = .TRUE.

USE of ICHARG = 11, ISTART=1, and NPAR=1 tag:
Then I run a single point job with the following INCAR

PREC = Normal
IBRION = -1
ENCUT = 400
EDIFF = 1.0e-06
ALGO = Normal (blocked Davidson)
ISPIN = 1
ISTART = 1
ICHARG = 11
ISMEAR = 0
SIGMA = 0.05
NPAR = 1
LREAL = AUTO
LCHARGE= .TRUE.
LOPTICS= .TRUE.

Then I use the vasprun.xml file to plot the graph by the plotoptics.sh file available at vaspwiki.
I want to know whether the procedure is correct or not. Can you suggest any modifications to better the results.

Hi,

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