[gmx-users] About the temperature coupling

[llshen]

Dear Lists:
As suggested, I heated up my system (containing SPC water molecular) step by step with step width 100K or some value else. When I checked the temperature curves, however, I found that at every step the temperature was first up to hear 300K and then cool down to the refer temperature I choosed. It forms a heating up shock on the system in very short period, and I think such shock makes the step by step heating up strategy meaningless.  Did anyone else note this phenomenon or is it an operation error of mine?  If not my errors, what's the intrinsic explaination to this? 
BTW, a sample of heating up *.mdp file is copied here:
;
;	User spoel (236)
;	Wed Nov  3 17:12:44 1993
;	Input file
;
title               =  Yo
cpp                 =  /lib/cpp
define              =  -DPOSRES
constraints         =  h-bonds
integrator          =  md
dt                  =  0.002	; ps !
nsteps              =  50000	; total 100 ps.
nstcomm             =  1
nstxout             =  500
nstvout             =  1000
nstfout             =  0
nstlog              =  100
nstenergy           =  10
nstlist             =  10
ns_type             =  grid
rlist               =  1.0
rcoulomb            =  1.0
rvdw                =  1.0
; Berendsen temperature coupling is on in two groups
Tcoupl              =  berendsen
tc-grps		    =  Protein	SOL  
tau_t               =  0.1	0.1 
ref_t               =  0	100  
; Energy monitoring
energygrps	    =  Protein	SOL
; Pressure coupling is not on
Pcoupl              =  no
tau_p               =  0.5
compressibility     =  4.5e-5
ref_p               =  1.0
; Generate velocites is on at 300 K.
gen_vel             =  yes
gen_temp            =  300.0
gen_seed            =  173529

Any suggestions?

Lingling Shen 
********************************************
Lingling Shen        		(Ph.D Student)
Drug Discovery and Design Center
Shanghai Institute of Materia Medica
Chinese Academy of Science
Shanghai 200031, China

Tel. 086-021-64311833-222
E-Mail: llshen at mail.shcnc.ac.cn
*********************************************