Dear David, I followed your instructions and calculated Heat of vaporization of my alkane once with one molecule in gas phase (no cutoff) and once with equivalent number of molecules as in liquid phase as Justin suggested. Results are as follows:
*one single molecule in gas phase* Energy Average Err.Est. RMSD Tot-Drift ------------------------------------------------------------------------------- LJ (SR) -2.24473 0.073 1.292 0.342696 (kJ/mol) Coulomb (SR) 11.5723 0.55 2.17577 -2.33224 (kJ/mol) Potential * 59.244 * 0.94 10.9756 6.35631 (kJ/mol) Total Energy 106.647 1 15.4828 6.78792 (kJ/mol) *equivalent number of molecules as in liquid* ( large box 20 nm) Statistics over 1000001 steps [ 0.0000 through 2000.0000 ps ], 4 data sets All statistics are over 100001 points Energy Average Err.Est. RMSD Tot-Drift ------------------------------------------------------------------------------- LJ (SR) -2.16367 0.053 0.171542 0.374027 (kJ/mol) Coulomb (SR) 11.2894 0.23 0.49105 -1.44437 (kJ/mol) Potential * 63.2369 * 1.1 2.47211 7.69756 (kJ/mol) Total Energy 114.337 1.1 2.65547 7.72258 (kJ/mol) Since pbc is set to NO molecules leave the box and I dont know if this all right. I hope the difference is acceptable...! 0- I am going to do the same calculation but for some polymers solvated in the alkane. For binary system do I need to look at nonboded terms? and then run a simulation for a single polymer in vacuum? Can you please provide me with a recipe for Delta Hvap of the solute in a solvent? 1- If I want to look at nonboded interactions only, do I have to add Coul. recip. to [ LJ (SR) + Coulomb (SR) ] ? coulombtype = PME vdw-type = Shift rcoulomb-switch = 0 rvdw-switch = 0.9 rlist = 1.2 rcoulomb = 1.2 rvdw = 1.0 ff: OPLSAA Appreciate your help, Best,
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