Hello everybody,
I run 2 optimization calculations for (adsorbent+adsorbate) with the same conditions, only the unit cells kpoint of them was different. That is, they were in the same orientation and position before the opt.

The first unit cell with 10x10×1 kpoint and the second unit cell with 4x4×1 kpoint were optimized.  I chose the supercell made of them with 4x4×1 kpoint. 
In the first structure, the bond lenght increased greatly and abnormally and in the second calculation, the bond length of the absorbate did not increase much.

⭕️ My first question is this: is this sharp increase in the bond lenght due to the high unit cell kpoint 10×10×1?  (The rest of the parameters of the two calculations are the same.)

⭕️The second question is, how do I know which calculation is correct?  The one whose adsorbate bond length has increased a lot or the one whose bond has not changed much?

Thank you for your guidance.