# Simulated Tempering stuck at lowest temperature

**URL:** <https://gromacs.bioexcel.eu/t/simulated-tempering-stuck-at-lowest-temperature/2121>\
**Category:** User discussions\
**Created:** [May 7, 2021, 7:37pm UTC](https://gromacs.bioexcel.eu/t/simulated-tempering-stuck-at-lowest-temperature/2121 "2021-05-07T19:37:22Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![amin\_sagar](https://avatars.discourse-cdn.com/v4/letter/a/a87d85/32.png) [@amin\_sagar](https://gromacs.bioexcel.eu/u/amin_sagar)\
**Post date:** [May 7, 2021, 7:37pm UTC](https://gromacs.bioexcel.eu/t/simulated-tempering-stuck-at-lowest-temperature/2121/1 "2021-05-07T19:37:22Z")

</div>

GROMACS version: 2021.1  
GROMACS modification: No  
Dear GROMACS users/developers,  
I am trying to do some simulated tempering simulations on a protein with explicit solvent (TIP4P-D).  
I am using a temperature range of ~ 293 to 410 K. However, the temperature doesn’t change during the simulation and the system stays at the lowest temperature of 293 K. The same can be seem in the final weights.  
MC-lambda information  
Wang-Landau incrementor is: 1  
N Temp.(K) Count G(in kT) dG(in kT)  
1 293.150 2000 0.00000 2000.00000 \<\<  
2 299.000 0 2000.00000 0.00000  
3 304.850 0 2000.00000 0.00000  
4 310.700 0 2000.00000 0.00000  
5 316.550 0 2000.00000 0.00000  
6 322.400 0 2000.00000 0.00000  
7 328.250 0 2000.00000 0.00000  
8 334.100 0 2000.00000 0.00000  
9 339.950 0 2000.00000 0.00000  
10 345.800 0 2000.00000 0.00000  
11 351.650 0 2000.00000 0.00000  
12 357.500 0 2000.00000 0.00000  
13 363.350 0 2000.00000 0.00000  
14 369.200 0 2000.00000 0.00000  
15 375.050 0 2000.00000 0.00000  
16 380.900 0 2000.00000 0.00000  
17 386.750 0 2000.00000 0.00000  
18 392.600 0 2000.00000 0.00000  
19 398.450 0 2000.00000 0.00000  
20 404.300 0 2000.00000 0.00000  
21 410.150 0 2000.00000 0.00000  
The total simulation length was 4 ns just to check if everything was working as expected.  
My mdp file is pasted below. I would really appreciate any suggestions to make the system explore other temperatures.

## Amin. mdp file

integrator = md-vv  
dt = 0.002  
nsteps = 2000000  
nstxtcout = 2500  
nstvout = 250000  
nstfout = 250000  
nstcalcenergy = 1000  
nstenergy = 1000  
nstlog = 1000  
;  
cutoff-scheme = Verlet  
nstlist = 20  
rlist = 1.0  
coulombtype = pme  
rcoulomb = 1.0  
vdwtype = Cut-off  
;vdw-modifier = Force-switch  
;rvdw\_switch = 1.0  
rvdw = 1.0  
DispCorr = EnerPres  
;  
; Temperature coupling is on  
tcoupl = V-rescale ; modified Berendsen thermostat  
tc-grps = Protein Non-Protein ; two coupling groups - more accurate  
tau\_t = 0.1 0.1 ; time constant, in ps  
ref\_t = 293.15 293.15 ; reference temperature, one for each group, in K  
;  
pcoupl = berendsen  
pcoupltype = isotropic  
tau\_p = 5.0  
compressibility = 4.5e-5  
ref\_p = 1.0  
;  
constraints = h-bonds  
constraint\_algorithm = LINCS  
lincs-iter = 2  
lincs-order = 6

continuation = yes  
;  
nstcomm = 100  
comm\_mode = linear  
comm\_grps = SYSTEM  
;  
refcoord\_scaling = com

;Simulated tempering  
nstexpanded = 1000  
simulated-tempering = yes  
sim-temp-low = 293.15  
sim-temp-high = 410.15  
simulated-tempering-scaling = linear  
init\_lambda\_state = 0  
temperature\_lambdas = 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00  
lmc-stats = wang-landau  
lmc-move = metropolized-gibbs  
lmc-weights-equil = wl-delta  
weight-equil-wl-delta = 0.001  
wl-scale = 0.7  
wl-ratio = 0.8  
init-wl-delta = 1.0  
wl-oneovert = yes