On 6/20/13 11:11 PM, Hari Pandey wrote:
Hi all  gromacs users

I have following (NVT.mdp) (NPT.mdp)  and (NVE.mdp)   .  I have three parts of 
system, A, B and C.
I want to put thermostat on A and C and couple the tempereture and do not put 
any thermostat on B.

What I want is: after some ps,  temperature of A and C should be constant (i.e 
reach up to steady state) and  B may not be.

for that My NVT.mdp is:
; simulation at 300K and 2 ps is on
         constraints     =all-bonds
         integrator      =md
         dt              =0.001 ; ps
         nsteps          =100000 ; total 100 ps
         nstcomm         =10
         nstxout         =1000
         nstxtcout       =0

  nstvout         =0
         nstfout         =0
         nstenergy       =100
         nstlist         =100
         ns_type         =grid
         rlist           =0.5
         coulombtype     =pme
         rcoulomb        =0.5
         vdwtype         =cut-off

  rvdw            =0.5
         pme_order       =4
         ewald_rtol      =1e-5
         optimize_fft    =yes
         DispCorr        =no


;Brendsen tempereture coupling is on
         Tcoupl          = nose-hoover
         tau_t           =0.001
  -1   0.001
         tc-grps         =A  B   C

         ref_t           =750      300       350


;pressure coupling is on
         Pcoupl          =no
         Pcoupltype      =isotropic
         tau_p           =0.5
         compressibility =1e-5
         ref_p           =0.5
;generate velocities at 300 k i.e. at room
  tempereture
         gen_vel         =yes
         gen_temp        =750  300  350
         gen_seed        =-1

MY NPT.mdp is:

( here all output control parameters also)


;Brendsen tempereture coupling is on
         Tcoupl          =nose-hoover
         tau_t           =1  -1   1
         tc-grps
  =NCALPHA MIDDLE NCNN
         ref_t           =750  300 350



;pressure coupling is on
         Pcoupl          =Berendsen
         Pcoupltype      =isotropic
         tau_p           =0.5
         compressibility =1e-5
         ref_p           =1
;generate velocities at 300 k i.e. at room tempereture
         gen_vel         =no

  gen_temp        =750 300 350
         gen_seed        =-1

MY NVE.mdp is:
( here all output control parameters also)
   tc-grps         = A  B  C

  ref_t           =750 300 300
         energygrps      = NCALPHA  MIDDLE  NCNN
         tcoupl         = nose-hoover
         tau-t          = 1  -1   1
;pressure coupling is on
         Pcoupl          =no
         ;Pcoupltype      =isotropic
         ;tau_p           =0.5
         ;compressibility =1e-5

  ;ref_p           =0.5
;generate velocities at 300 k i.e. at room tempereture
         gen_vel         =no
       ;  gen_temp        =750  300  350
        ; gen_seed        =-1



What I did is:

pdb2gmx - argnew.pdb -o fws.pdb -p  fws.top;
editconf -f fws.pdb -bt dodecahedron -o fws.pdb -d 1.0;
grompp-f em.mdp -c fws.pdb -p fws.top -n index.ndx -o em.tpr -maxwarn 5;
mdrun -deffnm  em -v;
grompp -f nvt.mdp -c em.gro -p fws.top -n index.ndx  -o nvt.tpr -maxwarn 5;
mdrun -deffnm nvt -v;
grompp -f npt.mdp -c nvt.gro -p fws.top -n index.ndx  -o npt.tpr -maxwarn 5;
mdrun -deffnm npt -v
grompp -f nve.mdp -c npt.gro -p fws.top -n index.ndx  -o nve.tpr -maxwarn 5;
mdrun -deffnm nve -v;

g_energy -f nve.edr -s nve.tpr -o F1.xvg



But the system do not get equilibrated and A, B has not steady state 
temperature  after   time
  even 100 ps. please help me, where I did wrong


See my previous reply:

http://lists.gromacs.org/pipermail/gmx-users/2013-June/082392.html

-Justin

--
========================================

Justin A. Lemkul, Ph.D.
Research Scientist
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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