How to calculate ionization potential and electron affinity?

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YunLi · #1 Post by **YunLi** » Thu Apr 22, 2010 4:37 am

I tried to do some calculation for organic semiconductor,pentacene. By following the defination, Eip=E(-e)-E(neutral) and Ea=E(e+)-E(neutral), I gained a nagetive value of IP for pentacene crystal structure, which is against the positive value in reference,and a positive value for single molecule.
My INCAR file is showed below.
IALGO = 38
NWRITE = 3
PREC = HIGH
ENCUT = 500
LREAL = .TRUE.
NELM = 60
EDIFF = 1e-4
NSW = 0
ISPIN = 2
ISMEAR = 0
NELECT = 203(the # of neutral = 204)
Ionic relaxarion
ISIF = 3
EDIFFG = -0.01
IBRION = 2
ISYM = 0
POTIM = 0.5

Please help me to figure this out. Thanks . :@

tlchan · #2 Post by **tlchan** » Thu Apr 22, 2010 1:35 pm

You probably need to turn on the dipole correction.