<div dir="ltr">Dear CP2K community, I would like to simulate a small organic molecule, MethylGlyoxal, on a liquid water interface comprising of 216 water molecules.The total number of atoms in my simulation box is 657 atoms and 20 A X 20 A X 60 A size, with two liquid-water/vacuum interfaces along the z-direction.This system has been previously equilibrated by classical MD. I am writing you because I am not able to reach a reasonable convergence for the cutoff. On the other hand, the rel_cutoff the behavior looks reasonable. I am a bit puzzled because, looking at the literature, several works using liquid water slab were performed with cutoff of 280 Ry (or similar).Here, even with 400 Ry I cannot see a reasonable convergence. I tried to look in the mailing list, exploring different options but without success. You can find attached my input files.Moreover, how the performance of my runs would be affected using a large cutoff? Thank you very much for any possible help or hint.. I am a newbie in cp2k. Ivan ---------------:::::::::::::: # Grid cutoff vs total energy # Date: Tue Oct 4 15:14:43 AST 2016 # REL_CUTOFF = 60 # Cutoff (Ry) | Total Energy (Ha) | NG on grid 1 | NG on grid 2 | NG on grid 3 | NG on grid 4 150.00 -3601.3810732568 6355937 1954418 1677530 1532857 200.00 -3602.4707815085 5617861 2264331 1690695 1947855 250.00 -3603.0017495985 5385050 1981561 2003927 2150204 300.00 -3603.5954834995 4713771 2383273 1993480 2430218 350.00 -3603.8647277931 4575375 2443492 1787867 2714008 400.00 -3604.2212237954 4160605 2491335 2066041 2802761 450.00 -3604.4406345606 4014931 2341006 1954418 3210387 500.00 -3604.6475134416 3777337 2142718 2204241 3396446 550.00 -3604.8761360971 3647230 2133733 2123763 3616016 600.00 -3605.0089346664 3581670 2036191 2264331 3638550 650.00 -3605.2009691021 3505781 1965487 2039270 4010204 700.00 -3605.2009689802 2988139 2429724 1948748 4154131 750.00 -3605.4377935718 2895507 2489543 1981561 4154131 :::::::::::::: rel_cutoff_data.ssv :::::::::::::: # Rel Grid cutoff vs total energy # Date: Tue Oct 4 15:14:44 AST 2016 # CUTOFF = 400 # Rel Cutoff (Ry) | Total Energy (Ha) | NG on grid 1 | NG on grid 2 | NG on grid 3 | NG on grid 4 10.00 -3609.6346138640 315656 2541164 2201475 6462447 20.00 -3604.4859689279 1815123 2345482 2491335 4868802 30.00 -3604.2265167341 2856820 2201475 2302172 4160275 40.00 -3604.2214496779 3581670 2036191 2264331 3638550 50.00 -3604.2212362541 3921274 2123947 2079075 3396446 60.00 -3604.2212237954 4160605 2491335 2066041 2802761 70.00 -3604.2212216269 4595916 2422951 1787867 2714008 80.00 -3604.2212216266 4713771 2383273 1993480 2430218 90.00 -3604.2212216259 5058295 2302172 2010071 2150204 100.00 -3604.2212216259 5385050 1981561 2020317 2133814 -----------</div>