[gmx-users] Heating the system

[Christoph Freudenberger]

li weihua wrote:
> Hi,all
>   I am a new user for Gromacs. After minimization, I want to heat my 
> system from 0K ,100K,200K to 300K in a short period(e.g.30ps). However, 
> i don't know if it is right to set up the parameters of heat.mdp.  In 
> heat1.mdp:
>  ...
>  nsteps=5000
>  dt    =0.002
>  ref_t =0K
>  ...
>  In heat2.mdp:
>  ...
>  nsteps =5000
>  dt     =0.002
>  ref_t  =100K
>  ...
>  In heat4.mdp
>  nsteps =5000
>  dt     =0.002
>  ref_t  =300K
>  But,in the energy curve,I found that the energy reached the reference 
> temperature very fast,and then flutuated at the ref_t.
>  Are my .mdp file right?  Anyone can give me some help? Thank you very 
> much!
> 

there's nothing wrong with your mdp's, it's normal that ref_t is reached
within a few timesteps.
i'm just wondering why you do it that way.

If you just want to get the md started after em use:
ref_t=300, gen_vel=yes, gen_temp=300
(maybe use pressure coupling to allow scaling of the box)

If you really want to heat up slowly (for whatever reason)
use a larger value for tau_t.

regards
-- 
Christoph Freudenberger
Abt. Organische Chemie I AK Siehl - Uni Ulm -Tel: ++49-731-502-2785