My Community

Dear VASP users,

I performed a calculation of a H2 molecule in a cubic box with with 15 Angstrom side length (PAW-LDA, KPOINT is only at gamma). Optimized H2 structure was obtained with H-H bond length ~0.75 Angstrom.

When I looked at the KS-state (which I assumed to be its molecular orbitals) I found:

1 -10.1230 2.00000
2 -0.1507 0.00000
3 0.3449 0.00000
4 0.9644 0.00000
5 0.9644 0.00000

state #1 is H2 bonding state and #3 is H2 antibonding state (can look at charge density shape) The problem is I cannot identify the state #2, its charge density shape looks like #1. I am not sure if I missed any basic physics relating to H2 molecule.

PS. the state #2 also occur in SPIN polarized calculation.
also I varies size of cell and number of bands, state #2 is still exist

Thanks in advance!

When I calculated a single H atom, some strange atomic level occured

In case of N2 molecule, the KS-orbitals could be identified as ss_sigma (1), ss_sigma* (2), pp_pi(3,4), pp_sigma (5) as follows:
1 -28.0119 2.00000
2 -13.4489 2.00000
3 -11.3842 2.00000
4 -11.3842 2.00000
5 -10.0200 2.00000
6 -2.0450 0.00000
7 -2.0450 0.00000
So, anyone can shed me a light, what is the state #2 of H2?

Thanks again!