Hi everyone! Currently I do some research concerning adsorption of organic molecules on carbon structures and started to use Materials Studio. I have read the paper in the Journal of Physical Chemistry: Thermodynamic and Modeling Study of Thin n‑Heptane Films Adsorbed on Magnesium Oxide (100) Surfaces, 118, 3451−3458, 2014, dx.doi.org/10.1021/jp407651t and wanted to repeat the calculations as a test. I am very new to the software and I probably do some simple mistake so my calculations are far from anything reasonable. Could you be so kind and point me where is my mistake? If so this is what I do:

1. I create a slab of MgO from MS library. I cleave it along 1 0 0 with thickness 13,181 A.

2. I calculate forcefield parameters, delete bonds and relax surface with COMPASS Forcefield and Forcite.

3. I create a superlattice (17,866608 on 17,866608) and Vacuum Crystal out of it.

4. I optimize Heptane with COMPASS and pack it into a box 17,866608 on 17,866608 on 2.7 A using Amorphous Cell.

5. I combine using layers the MgO and Heptane system with 30 A vacuum.

6. I optimize again using COMPASS forcefield and motion group assigned to heptane (keep motion groups rigid in order to preserve heptane geometry, any other method?).

Trouble is I did many times and constantly I got non-bonded interactions around 75-78 kcal/mol being roughly 300 kJ/mol. I have to do some simple mistake and you probably understand my frustration. I would be greatly appreciated for some help and guidance. I send you the MS files from my project.

Lukasz