GROMACS version: 2019 and 2021
GROMACS modification: No
I am using acceleration groups in GROMACS extensively. (keywords: “acc-grps”, “accelerate”)
I was slightly surprised to read that “constant-acceleration MD” would be removed in GROMACS 2021 and that it has been broken for a long time, as my results seemed to make sense. Perhaps this is not exactly the same functionality as I have been using?
At any rate, I ran some trial runs where I had a water box with 1 Na+ and 1 Cl- ion, and I’d apply four forces in total:
1, 2) equal and opposite constant forces using the acceleration groups
3, 4) a restoring variable force with a spring on each ion (pull code)
As expected, the forces in 3, 4 match the ones in 1, 2 up to some small noise. So at least in my hands, the acceleration groups behaved as expected.
I would also like to add that I think the acceleration groups are a very useful feature, for example for adding a directional hydrostatic pressure. The pull code can only partially reproduce it, as if the acceleration group is sufficiently large, the definition of the COM will be error-prone.
As mentioned before though, maybe “Constant-acceleration MD” refers to another feature that I did not know about? In fact, I also ran my test with GROMACS 2021 and it worked as well, so maybe this is a misunderstanding on my part after all.
Thanks in advance!