Dear All: I have question about the pressure coupling. I have done a 10ns simulation with 19800 atoms for 120 large molecules using the following pressure coupling.
Tcoupl = berendsen tc_grps = PDM tau_t = 0.1 ref_t = 300 Pcoupl = berendsen pcoupltype = isotropic ;pc-grps = PDM tau_p = 1.0 ref_p = 1.0 compressibility = 4.5e-5 Then I did g_energy for the last 3ns and got the results: Energy Average RMSD Fluct. Drift Tot-Drift ------------------------------------------------------------------------------- Potential -98061 0 0 0.61668 1850.04 Temperature 303.561 109.602 109.602 0.000181791 0.545372 Pressure (bar) 4.4884 11110.8 11109.8 -0.169835 -509.506 For such a long run the pressure drift is still too much and seem hasn't approached 1bar. Does it mean the system hasn't reach equilibrium yet. I did a similar system by using the same method. it just take 2 or 3ns to reach the equilibrium. and the pressure is around 1.01after the run. The only difference is the cutoff changing from 1.2 to 1.4. Does the cufoff of 1.4 is too large to make the system running slower. Or the pressure coupling method is not working well. Anyone can give me any suggestions? -- Yanmei Song Ph.D. Candidate Department of Chemical Engineering Arizona State University
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