Hi all:
I was using Parrinello-Rahman for pressure coupling and here is the mdp
file:
; RUN CONTROL PARAMETERS =
integrator = sd
; start time and timestep in ps =
tinit = 0
dt = 0.001
nsteps = 200000
; number of steps for center of mass motion removal =
nstcomm = 100
; NEIGHBORSEARCHING PARAMETERS =
; nblist update frequency =
nstlist = 50
; ns algorithm (simple or grid) =
ns_type = grid
;OPTIONS FOR PRESSURE COUPLING
Pcoupl = Parrinello-Rahman
pcoupltype = anisotropic
tau_p = 1
compressibility = 2.1645e-09 2.1645e-09 2.7322e-09 0 0 0
ref_p = 1 1 1 0 0 0
;OPTIONS FOR TEMPERATURE COUPLING
tc_grps = system
tau_t = 0.1
ref_t = 300
; OPTIONS FOR BONDS =
constraints = hbonds
; Type of constraint algorithm =
constraint-algorithm = Lincs
; Do not constrain the start configuration =
unconstrained-start = no
; Relative tolerance of shake =
shake-tol = 0.0001
; Highest order in the expansion of the constraint coupling matrix =
lincs-order = 12
; Lincs will write a warning to the stderr if in one step a bond =
; rotates over more degrees than =
lincs-warnangle = 30
; Periodic boundary conditions: xyz, no, xy
pbc = xyz
periodic_molecules = no
; nblist cut-off
rlist = 1
; OPTIONS FOR ELECTROSTATICS AND VDW
; Method for doing electrostatics
coulombtype = PME
rcoulomb = 1
; Method for doing Van der Waals
vdw-type = Cut-off
; cut-off lengths
rvdw = 1
; Spacing for the PME/PPPM FFT grid
fourierspacing = 0.12
; FFT grid size, when a value is 0 fourierspacing will be used
fourier_nx = 0
fourier_ny = 0
fourier_nz = 0
; EWALD/PME/PPPM parameters
pme_order = 6
ewald_rtol = 1e-4
ewald_geometry = 3d
epsilon_surface = 0
optimize_fft = no
It seems that the temperature coupling is fast and fluctuation is less that
1%. But the pressure coupling fails. The pressure fluctuates from +1e3 bar
to -1e3 bar. Anyone can help?
Thanks,
Shuangxing Dai
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