Calculating the absorption energy involves simulating the interaction of a molecule or atom with a surface or material. The absorption energy (Eabs) is the energy difference between the system after absorption and the isolated components (e.g., the surface and the adsorbate).
Hi Boudabia Saad
Indeed, the adsorption energy (E_ads) can be calculated using total energy differences between the adsorbed system (slab+adsorbate), the clean surface (slab), and the isolated adsorbate. You can go through the following steps:
[1]. Build a slab model though a supercell adding a vacuum of about 20 A.
[2]. Perform a geometry optimization of the slab.
[3]. Perform a separate calculation for the adsorbate in a large vacuum box.
[4]. Put the adsorbate in the optimized slab and perform another geometry optimization.
[5]. Extract the energies, and do the math for E_ads using this Eq:
E_ads = E_system [4] - (E_adsorbate [3] + E_clean_surface [2])
Hope that helps,
Cheers
Thank you very much dear Gabriel for your answer, the problem is that I am a novice in CaASTEP and I don't know how to do it.
Anytime! Despite the similarities among DFT codes, I am not familiar with CASTEP. If you can use QE or VASP, I can assist you further.
Best,
Which part of the process don't you understand? Are you familiar with doing basic DFT calculations with CASTEP, for example bulk silicon?
@gabriel's answer is excellent, those are exactly the right calculations to perform, so if you explain where you need help I'm sure we can guide you.
All the best,
Phil Hasnip
(CASTEP developer)
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