[gmx-users] temperature too high with reaction field
gmx3 at hotmail.com
Wed Jan 21 17:57:46 CET 2009
This is normal.
Reaction-field still uses a cut-off, which gives cut-off errors.
To make the the error small you will need to reduce tau_t.
Or use reaction-field-zero with a buffer region (computationally expensive).
The real solution is to simply use PME.
> Date: Wed, 21 Jan 2009 17:51:02 +0100
> From: sam.moors at chem.kuleuven.be
> To: gmx-users at gromacs.org
> Subject: [gmx-users] temperature too high with reaction field
> Hi gmx users,
> I'm trying to simulate a water box filled with TIP3P water.
> With PME, everything seems OK.
> However, when I switch to reaction field electrostatics,
> the temperature in the output files is too high:
> 312K instead of 300K (the t_ref value for the whole system).
> Maybe there is something wrong with my input paramters?
> Below you find my .mdp file
> integrator = md
> dt = 0.002 ; ps !
> nsteps = 20000
> nstcomm = 1
> nstxout = 500
> nstvout = 0
> nstlog = 500
> nstenergy = 500
> nstfout = 0
> nstlist = 10
> ns_type = grid
> rlist = 1.2
> coulombtype = Reaction-Field
> epsilon_r = 1
> epsilon_rf = 78
> rcoulomb = 1.2
> table-extension = 1
> vdwtype = cutoff
> rvdw = 1.2
> fourierspacing = 0.19
> fourier_nx = 0
> fourier_ny = 0
> fourier_nz = 0
> pme_order = 4
> ewald_rtol = 1e-5
> optimize_fft = yes
> ; temperature coupling
> Tcoupl = v-rescale
> tau_t = 1.0
> tcgrps = system
> ref_t = 300
> ; Pressure coupling
> Pcoupl = parrinello-rahman
> tau_p = 1.0
> compressibility = 4.5e-5
> ref_p = 1.0
> ; Generate velocites
> gen_vel = no
> gen_temp = 300
> gen_seed = 173529
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