I am trying to simulate the following system: 5-layer FCC substrate consisting of Si particles which interact only with Lennard-Jones potential and vertical to the substrate I put polymer chains of (CH2-OA), starting from a distance of 0,4nm. What I want is to be able to manage completely independently the LJ interactions between the substrate and the polymers and not according to the combination rules, i.e. to have very very strong LJ interaction only between the Si particles but these to interact normally with the polymer chains. I use the Gromos-96 force-field. The initial values for the c6 and c12 parameters are the following: [ atomtypes ] name at.num mass charge ptype c6 c12 OA 8 0.000 0.000 A 0.0022619536 1.505529e-06 CH2 6 0.000 0.000 A 0.0074684164 3.3965584e-05 SI 14 0.000 0.000 A 0.01473796 2.2193521e-05 [ nonbond_params ] i j func c6 c12 SI OA 1 0.0000000 0.00000000 SI CH2 1 0.0000000 0.00000000 SI CH3 1 0.0000000 0.00000000 What I did is to run 2 different simulations in NVT ensemble. In the first, I multiplied by 10 the c6, c12 values of Si in the [atomtypes ] and in the second I multiplied (the initial values again) by 100. In both cases I didn’t change the values on the [nonbond_params ]. I would expect that in both cases there should be no adsorption of the polymers in the substrate, since I change the interaction between the substrate and the polymers in the [nonbond_params ] equal to zero. What I observed is that after 50000 steps with 2 fs time step the polymers in the second case adsorbed to the surface. Can anybody help me or explain me why is this happening? Thanks in advance Chrysostomos
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