[gmx-users] Incorrect SPC water density using oplsaa force field

[atb files]

            Hello Users,I tried simulating a water box (SPC) at 298 K and 1 bar pressure. I am not getting the correct value for water density. The literature value is 997 kg/^3 whereas I am getting the value of 977 kg/^3I am using Gromacs 2018.4Force field I used is oplsaa from used Gromacs version. I first did energy minimisation, then NVT and NPT simulation with Berendsen thermostat and barostat for 5 nanoseconds each. Then I did NPT following MDP file:






integrator	= md		
nsteps		= 500000 	
dt		= 0.002		
nstlog		= 5000 
nstxout-compressed = 500
nstenergy = 500
continuation	= yes		
constraint_algorithm = SHAKE	
constraints	= all-bonds   	
nstlist         = 10             
ns_type         = grid          
rlist           = 1           
rcoulomb        = 1           
rvdw            = 1           
; Electrostatics
coulombtype     = PME           
pme_order       = 4                 
fourierspacing  = 0.16          
pbc		= xyz 		
tcoupl		= v-rescale		
tc-grps	        = System   		
tau_t		= 1.0   			
ref_t		= 298.15 		
pcoupl		= parrinello-rahman	
pcoupltype	= isotropic		
tau_p		= 5.0 		
ref_p		= 1.0 1.0 	        
compressibility = 4.6e-5 4.6e-5       
DispCorr	= EnerPres	
gen_vel		= no		
gen-temp	= 298.15
gen-seed	= 121545
refcoord_scaling = comIs there something wrong with my MDP file? Cutoffs and all? Please help.- YogeshSent using Zoho Mail