Dear all, I noticed that applying Parrinello-Rahman (PR) pressure coupling even after equilibration with berendsen does not lead to target value for pressure when
; Bonds constraints = none is used. I tried Berendsen for to get fixed pressure ( 50 bar) but in the next run PR even for long time is giving 52 bar. This is the case for other target pressures too. So this made me select Berenden which is giving target pressure values but my concern is whether my results are reliable because BR does not give the exact ensemble as PR. I read somewhere on the list that fluctuation properties can not be calculated when BR is used. What does "fluctuation property" mean? Does this mean that any property calculated form fluctuations of some other quantity can not be obtained>? like heat capacity which is defined based on enthalpy fluctuations? I am interested in potential energy terms (g_energy bonded/non boned terms) and structural properties like rdf for a number of polymer molecules, system size around 3000 atoms. Thank you for your comments. Best, constraints = none ; Run control integrator = md dt = 0.002 nsteps = 5000000 nstcomm = 100 nstenergy = 100 nstxout = 100 nstlist = 10 ns_type = grid coulombtype = Shift vdw-type = Shift rcoulomb-switch = 0 rvdw-switch = 0.9 ;0 ; Cut-offs rlist = 1.25 rcoulomb = 1.0 rvdw = 1.0 Tcoupl = v-rescale tc-grps = System tau_t = 0.1 ref_t = 300 Pcoupl = berendsen Pcoupltype = isotropic tau_p = 1 compressibility = 3.5e-5 ref_p = 10 gen_vel = no gen_temp = 300.0 gen_seed = 173529
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