[QE-users] Wrong adsorption energy

[Laurens Siemons]

Dear all,


I'm calculating parameters like adsorption energy, geometric parameters, NMR chemical shifts of adsorbates on a surface. In this specific case I calculated the adsorption energy of an ethyl anion on an anatase 001 surface of titania. I got the following energies:


Esurface + adsorbate = -4301.05337244

Esurface = -4258.9387474

Eadsorbate = -42.37757742


So Eads = Esurface + adsorbate - (Esurface + Eadsorbate) = 0.26


Now this seems wrong. If Eads is positive, so adsorption is not favourable, then the ethyl-anion should migrate away from the surface in the relax calculation of a001cti. correct? I executed the three calculations with the exact same parameters as the other ones so I don't see how this is possible. I attached my input files of the calculations. I hope someone can guide me through this.


Thanks in advance,

Laurens Siemons

Master student chemistry

University of Antwerp

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