Calculating binding energy

[Oksana Grinevich]

I am running calculations to obtain binding energy of a molecule on the graphene sheet. After obtaining the energy value of this system (bonded), I calculate the energy values for lone molecule and lone graphene atoms (I tried with the same coordinates and varying them). Thus, I can roughly find the excess (adsorption) energy as follows:

E (excess)=E(bonded)-E(lone molecule)-E(lone graphene)

After this step I want to convert this energy to kJ/mol (*2625.5). It worked pretty well for benzene on graphene (obtained 40 kJ/mol) and other aromatic structures but for ammonia and triethylamine I can obtain something like 700 kJ/mol or even more which seems not physically corrected values.

I would like to know where I did wrong and what can I do to improve results.

[Quentin Pessemesse]

Hello,

Could you please send the .inp files so that I can have a look ? It looks like maybe something went wrong with the geometry optimization of either your lone components or your adduct.

Best,

Quentin

[Oksana Grinevich]

nh3_last - optimization file

nh3last_1 - energy for optimized geometry of bonded system

nh3last_3 - energy for optimized geometry of lone graphene

nh3G24_2 - energy of lone ammonia on a distance (imitation of infinity distance)

воскресенье, 2 марта 2025 г. в 22:41:59 UTC+3, Quentin Pessemesse:

[Quentin Pessemesse]

Hello again,

Maybe I'm visualizing wrong, but it looks to me like the "adsorbed" ammonia molecule did not optimize to the structure you wanted. It looks like you have a molecule split on either side of the graphene sheet. If this is what you meant to do, it's fine, otherwise you need to rebuild it. It looks like you did not re-optimize either the ammonia molecule or the graphene sheet, which you must do if you want to have meaningful energetics. Right now, you are seeing that starting from an extremely distorted NH3 and a distorted graphene, it is much much favorable to adsorb on graphene, which makes sense but does not give you the information you want.

Take care :)

Quentin

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