Hi Gromacians I want to do equilibration of water (spc model) first in the NVT ensemble and then in the NPT ensemble to maintain a temperature of 300K and a pressure of 1 bar respectively. The NVT equilibration works fine and the average temperature turns out to be 299.229 K.
Energy Average RMSD Fluct. Drift Tot-Drift ------------------------------ ------------------------------------------------- Temperature 299.229 10.3092 10.2463 0.0393873 3.93877 Heat Capacity Cv: 12.494 J/mol K (factor = 0.00118698) when i do NPT equilibration i am not getting the desired pressure as 1 bar or atleast close to 1 bar (between 1-1.4 bar). In the mdp file i used semiisotropic pressure coupling type because i want to fix the length of the box same on two axis as that of the original box size and want to change it only on one axis. can any one tell me why iam not getting the desired pressure of 1 bar?. Energy Average RMSD Fluct. Drift Tot-Drift ------------------------------------------------------------------------------- Pressure (bar) 7.4339 574.052 573.574 0.812129 81.2138 Given below is my mdp file (NPT equilibration). any help is highly appreciated. title = DCE NVT equilibration cpp = usr/bin/cpp integrator = md nsteps = 100000 dt = 0.001 nstxout = 100 nstvout = 100 nstenergy = 100 nstlog = 100 ns_type = grid nstlist = 1 rlist = 1.0 coulombtype = PME rcoulomb = 1.0 vdwtype = Cut-off rvdw = 1.0 pme_order = 4 fourierspacing = 0.16 pbc = xyz tcoupl = V-rescale tc-grps = system tau_t = 0.1 ref_t = 300 pcoupl = berendsen pcoupltype = semiisotropic tau_p = 0.5 ref_p = 1.0 1.0 compressibility = 0.0 4.5e-5 DispCorr = Enerpres gen_vel = yes gen_temp = 300 gen_seed = 173529 Regards Vinoth
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