[gmx-users] problem with the size of freeze groups
Berk Hess
gmx3 at hotmail.com
Fri Feb 26 17:01:39 CET 2010
Ah, but that does not correspond to the mdp options tou mailed.
Here there is only one group with 0 degrees of freedom and reference temperature 0.
Berk
Date: Fri, 26 Feb 2010 10:50:13 -0500
Subject: Re: [gmx-users] problem with the size of freeze groups
From: jampanis at gmail.com
To: gmx-users at gromacs.org
HI
Thanks, My log file shows me "nrdf: 0"
###############
grpopts: nrdf: 0 ref_t: 0
tau_t: 0
###############
ThanksSrinivas.
On Fri, Feb 26, 2010 at 10:25 AM, Berk Hess <gmx3 at hotmail.com> wrote:
Hi,
Then I have no clue what might be wrong.
Have you check nrdf in the log file?
Berk
Date: Fri, 26 Feb 2010 09:54:22 -0500
Subject: Re: [gmx-users] problem with the size of freeze groups
From: jampanis at gmail.com
To: gmx-users at gromacs.org
Dear Berk,
Thanks for your response, As you mentioned i have separated t-coupling group for frozen and non-frozen groups, still the result is same.Herewith i am giving my md.mdp file, Can you suggest me if i am missing any options in my md.mdp file?
Thanks againSrinivas.
md.mdp file
+++++++++++++++++++++++++++++++++++++++++++++++title = AB2130
cpp = /usr/bin/cpp
constraints = all-bonds
integrator = md
dt = 0.002 ; ps !
nsteps = 1500000 ; total 3.0 ns.
nstcomm = 1
nstxout = 1000 ; collect data every 2.0 ps
nstvout = 1000 ; collect velocity every 2.0 ps
nstfout = 0
nstlog = 0
nstenergy = 1000 ; collect energy every 2.0 ps
nstlist = 10
ns_type = grid
rlist = 1.0
coulombtype = PME
rcoulomb = 1.0
rvdw = 1.0
rvdw_switch = 0.9
fourierspacing = 0.12
fourier_nx = 0
fourier_ny = 0
fourier_nz = 0
pme_order = 4
ewald_rtol = 1e-5
optimize_fft = yes
; Berendsen temperature coupling is on in two groups
Tcoupl = V-rescale
tau_t = 0.1 0.1
tc-grps = Tmp1 Tmp2
ref_t = 300 0
gen_vel = yes
gen_temp = 300.0
acc_grps = Tmp2
accelerate = 0.1 0.1 0.1
gen_seed = 173529
freezegrps = Tmp2
freezedim = Y Y Y+++++++++++++++++++++++++++++++++++++++++++++++
On Fri, Feb 26, 2010 at 6:25 AM, Berk Hess <gmx3 at hotmail.com> wrote:
Hi,
It seems there is a bug in grompp, which subtracts degrees of freedom for
constraints in water also for frozen water molecules.
I guess the md.log file reports zero degrees of freedom for your t-coupl group.
You can circumvent this issue by putting all your frozen atoms in a separate
t-coupling group.
Berk
Date: Wed, 24 Feb 2010 21:34:30 -0500
From: jampanis at gmail.com
To: gmx-users at gromacs.org
Subject: [gmx-users] problem with the size of freeze groups
Dear Gromacs Users,
I would like to compare the diffusion coefficient of water in different confined spheres with the bulk solvent, I have taken a solvent box of size 7nm, and I have created a sphere with radius 25 Å as lowest and 35 Å as highest spheres. I have not used the pressure coupling for MD, and temp coupling is applied for freezing and non freezing waters separately. In case of the bigger sphere (i. e, 35 Å) the diffusion coefficient is 2.4 10-5 cm2/s (comparable with bulk), but the system with 25 Å radius gives me almost 0 diffusion coefficient. When I open the log file of 25 Å system it shows the initial temperature as zero.
Is there any relation between size of freezing group and temperature coupling? How the sphere with 35 Å radius is working fine but not with the radius 25 Å?
Can anybody help me?
Here is my m.mdp file
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
title = AB2130
cpp = /usr/bin/cpp
constraints = all-bonds
integrator = md
dt = 0.002 ; ps !
nsteps = 1500000 ; total 3.0 ns.
nstcomm = 1
nstxout = 1000 ; collect data every 2.0 ps
nstvout = 1000 ; collect velocity every 2.0 ps
nstfout = 0
nstlog = 0
nstenergy = 1000 ; collect energy every 2.0 ps
nstlist = 10
ns_type = grid
rlist = 1.0
coulombtype = PME
rcoulomb = 1.0
rvdw = 1.0
rvdw_switch = 0.9
fourierspacing = 0.12
fourier_nx = 0
fourier_ny = 0
fourier_nz = 0
pme_order = 4
ewald_rtol = 1e-5
optimize_fft = yes
; Berendsen temperature coupling is on in two groups
Tcoupl = V-rescale
tau_t = 0.1 0.1
tc-grps = Tmp1 Tmp2
ref_t = 300 0
gen_vel = yes
gen_temp = 300.0
acc_grps = Tmp2
accelerate = 0.1 0.1 0.1
gen_seed = 173529
freezegrps = Freez
freezedim = Y Y Y
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
--
*********************************************
J. Srinivasa Rao
Post-doctoral Research Associate
Computational Biophysics Group
Department of Physics
Drexel University
3141 Chestnut St
Philadelphia, PA 19104
Ph: Off: 215-895-1989
Mob: 704-706-4191
Web:http://jsrao.web.officelive.com/default.aspx
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C/o Prof. Luis R Cruz Cruz
Computational Biophysics Group
Department of Physics
Drexel University
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Please search the archive at http://www.gromacs.org/search before posting!
Please don't post (un)subscribe requests to the list. Use the
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*********************************************
J. Srinivasa Rao
Post-doctoral Research Associate
C/o Prof. Luis R Cruz Cruz
Computational Biophysics Group
Department of Physics
Drexel University
3141 Chestnut St
Philadelphia, PA 19104
Ph: Off: 215-895-1989
Mob: 704-706-4191
Web:http://jsrao.web.officelive.com/default.aspx
**********************************************
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