Thank you very much for your insightful answer!
Yes, I meant picoseconds not nanoseconds.
Perfect than I will try v-rescale as a thermostat and c-rescale as a barostat.
For the combination of v-rescale as thermostat and c-rescale as barostat is there any condition for the ratio of tau_p/tau_t that needs to be fulfilled (such as tau_p >= 2* tau_t when using NH and PR)?
I would really like to use the increased values for nsttcouple and nstpcouple so I would increase my tau_p and tau_p value respectively.
Regarding c-rescale, I could find the option in the in the GROMACS 2023 documentation but I couldn’t find any information about the algorithm in the current reference manual.
I assume though it is a first order coupling.
Based on that, first order couplings should be at least 5 times higher than (nstpcouple *dt) or (nsttcouple * dt) I would assume that with a time step of 2 femtoseconds the tau_p and tau_t should be at least 1 picosecond.
Would it be advisable to use the same value for tau_p as for tau_t? From my experience the tau_p value was always a multiple larger than the tau_t. But to be fair I never knew the explicit reason for that and went with the values generated and recommended by CHARMM-GUI.
Also, I recall reading, that higher values for tau_p and tau_t are preferred because they reduce the “bias” that is introduced by the barostat and thermostat. But again, I do not really know which value for tau_p and tau_t would be considered too high or too low. I basically just follow the recommendations in the GROMACS manual to determine the smallest accepted value.
Is there any guideline or a rule of thumb to determine the “right” value for tau_p and tau_t depending of the corresponding barostat and thermostat, besides the recommendation for the smallest accepted values in the GROMACS manual? I searched all the literature I could find but did not get a satisfying answers.
Based on you input I would adjust my mdp file as follows:
dt = 0.002
tcoupl = v-rescale
tc_grps = PROT_LIG MEMB SOLV
tau-t = 1.0
ref-t = 310 310 310
nsttcouple = -1 # It should be adjusted to 100
pcoupl = c-rescale
pcoupletype = semiisotropic
tau-p = 1.0
compressibility = 4.5e-5 4.5e-5
ref-p = 1.0 1.0
nstcouple = -1 # It should be adjusted to 100
Key question: which tau_p and tau_t values are recommended to run a simulation of a membrane bound protein using v-rescale as thermostat and c-rescale as a barostat using GROMACS 2023.0?