Hi, I am trying to run in NVT and get surface tension of polystyrene film in the top and bottom vacuum layer.
I also have another film system where the top, bottom, and middle vacuum layer is between the polymer.
The system is elongated in the Z direction.
I don’t want to run in NPT as it changes volume.
Semiisotropic is used for NPT, where compression in the xy direction isas per my understanding.
I used the below gro.mdp without semi-isotropic P coupling type for NVT.
I got average surface tension from the gmx energy command: #surf*surf_tension 340bar.nm
For single films with top and bottom vacuum layers, if I divide this value by 2, it will be 170bar.atm at 500K.As per the literature, it must be around 25mN/m.
I need to know if what I am doing to extract surface tension is correct. Please advise.
integrator = md
dt = 0.002
nsteps = 1500000000
nstxout = 500000
nstvout = 500000
nstfout = 0
nstlog = 500000
nstenergy = 100
nstcalcenergy = 100
nstxout-compressed = 500000
compressed-x-precision = 1000
cutoff-scheme = Verlet
ns_type = grid
rlist = 1.2 ; 12σ = 1.2 nm
rcoulomb = 1.2
rvdw = 1.2
verlet-buffer-tolerance = -1
coulombtype = PME
pme-order = 4
fourierspacing = 0.12
ewald-geometry = 3dc
vdw-type = Cut-off
vdw-modifier = Potential-shift-Verlet
pbc = xyz
tcoupl = V-rescale
tc-grps = System
tau_t = 0.1
ref_t = 500
pcoupl = no
epsilon-r = 1
constraint_algorithm = lincs
constraints = H-bonds
;gen_vel = no
;continuation = yes
comm-mode = Linear
nstcomm = 100
gen-vel = yes
gen-temp = 500
gen-seed = 173529
energygrps = System