Dear experts, I am intending to calculate the equilibrium density of a pure hydrocarbon at different pressures , at 425 K. The normal boiling point of the liquid is around 350 K. For pressures below 100 bar densities I am getting from NPT is in accurate. I start form a structure which is compressed to above 0.6 g/cm3 density but since temperature is high density goes than to the values below.
P = 50 bar > NPT rho= 0.344 experimental density ~ 0.54 P 100 > NPT rho= 0.43 experimental density ~ 0.55 densities become more accurate for P >100 bar. P 500 > rho= 0.56 experimental density ~ 0.61 I thought maybe you have some idea on how this inaccuracy can be improved. Thank you in advance for your invaluable help. Best, ; Bonds constraints = none constraint-algorithm = lincs ; Run control integrator = md dt = 0.001 nsteps = 5000000 nstcomm = 100 ; Output control nstenergy = 100 nstxout = 100 nstvout = 0 nstfout = 0 nstlog = 1000 nstxtcout = 1000 ; Neighbor searching nstlist = 10 ns_type = grid ; Electrostatics/VdW coulombtype = Shift vdw-type = Shift rcoulomb-switch = 0 rvdw-switch = 0.9 ; Cut-offs rlist = 1.25 rcoulomb = 1.0 rvdw = 1.0 ; Temperature coupling Tcoupl = v-rescale tc-grps = System tau_t = 0.1 ref_t = 425 ; Pressure coupling Pcoupl = berendsen Pcoupltype = isotropic tau_p = 1 compressibility = 3.5e-5 ref_p = 100 ; Velocity generation gen_vel = no;yes gen_temp = 425 gen_seed = 173529
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