Hello Everyone!

I am trying to calculate the change in Gibbs free for the adsorption of an atom on the two-dimensional sheet using VASP code. I have calculated adsorption energy values, however, I need to calculate zero-point energy and entropy.

In the previous few discussions, I found that to calculate zero-point energy following flags to be used to compute vibrational frequencies:

IBRION = 6

NSW = 1

NFREE = 2

The summation of all the energy values corresponding to every vibrational mode will give zero-point energy correction.

I have following queries regarding this:

1. Is the above-mentioned INCAR correct to compute zero-point energy?

2. Zero-point correction is the difference in the atom in the adsorbed phase and the molecule in gas phase. In order to calculate the value for atom in adsorbed state, do I need to take a difference between atom-adsorbed on sheet and sheet without hydrogen?

Thanks in advance for making my vision clear regarding this concept.