Why do you use NVT before NPT in some simulations?

GROMACS version: 2018.4
GROMACS modification: No
I have a question. I simulate pure bilayers systems (without proteins only lipids). Here I see that you use NVT equilibration KALP-15 in DPPC ant then NPT. So the only benefit for using NVT is a shorter equilibration time? I saw that people use only NPT equilibration and everything is fine. Why we should use NVT equilibration, in which cases? In my bilayer system which consists of 134 MGDG lipids, 66 DGDG lipids, and 6000 water molecules is it ok to use only NPT equilibration? Something bad could happen with my system if I use only NPT?

Using NVT before NPT often sorts out most cases in which the simultaneous generation of velocities and application of a barostat would lead to instability. GROMACS actually warns about this, hence why it is somewhat more robust to do two phases of equilibration, but it is by no means required.

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Thank you so much!