HOMO- LUMO gap

[Isha]

How to calculate HOMO-LUMO gap iin VASP?

[metosa]

Make a VASP calculation

Examine the energies in OUTCAR. You will easily find the answer by yourself .....

[jlbettis]

First: add "LORBIT = 11" and "ISPIN = 1" to your INCAR
Second: run a SCF calculation

Lastly you must decipher the DOSCAR file printed. Your DOSCAR should look like
"72 72 1 0
0.127E+02 0.770E-09 0.773E-09 0.153E-08 0.5000000E-15
1.0000000000000000E-004
CAR
XXXXXXX
20.00 -20.00 301 3.00609028 1.00
-20.000 0.2400E+03 0.3200E+02 <--Start plotting from here
-19.867 0.0000E+00 0.3200E+02
-19.733 0.0000E+00 0.3200E+02
-19.600 0.0000E+00 0.3200E+02
-19.467 0.0000E+00 0.3200E+02
-19.333 0.0000E+00 0.3200E+02
-19.200 0.0000E+00 0.3200E+02
-19.067 0.0000E+00 0.3200E+02"

The Bold Highlighted RED number is the Fermi level...
The 1st colunm is the Total energy in eV
The 2nd column is the Total DOS at that Energy

Plot columns one and two, omitting the line with the highlighted number and everything above that line"... put a vertical line at the Fermi level, and you should see band gap, assuming you have calculated a semi-conductor or insulator.

good luck

If you're not calculating a solid then you should listen to the first dude and check ya OUTCAR thinking maybe occupancy... I dunno for a molecule... I should find out though =)
<span class='smallblacktext'>[ Edited Wed Dec 01 2010, 05:23AM ]</span>

[M Dave]

Hi, I wanted to calculate HOMO-LUMO gap for atomic cluster. Can Any one please guide?

[M Dave]

Hi, I wanted to calculate HOMO-LUMO gap for atomic cluster. Can Any one please guide?

[admin]

Make a cluster in a large cell (e.g. 15A cube). Perform Gamma calculation. From band energies calculate HOMO-LUMO gap.

[M Dave]

Thanks admin.