[gmx-users] why temperature result of DMSO simulation is so low

[wang kelvin]

Hi



I am doing simulation of the mixture of DMSO and water . I put 512 DMSO
moleculers and 917 water moleculers in a box . The given temperature is 290K
, and pressure is 1 bar .

After simulation completed , I used g_traj to produce xvg file , then I saw
that simulation gave a temperatue result of about 200K.

Some documents tell me DMSO simulation usually gives 5-7 K lower than you
have given in mdp file ,e.g. if you give 300K in mdp file , but simulation
result gives 295 K .

I wonder why my simulation gave so low temperture ,any hints is appreciated.


Part of my mdp file:





Tcoupl                   = berendsen

tau_t               = 0.1 0.1

tc-grps         = DMSO SOL

ref_t               = 290 290

; Pressure coupling is not on

Pcoupl = parrinello-rahman

tau_p = 0.5

compressibility = 4.5e-5

ref_p = 1.0

; Generate velocites is on at 190 K.

gen_vel = yes

gen_temp = 290.0

gen_seed = 173529
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