Triclinic box vectors in a gro file

GROMACS version: 5.0.7
GROMACS modification: Yes/No
Hi. I want to simulate a triclinic box. The basis vectors and the angles of the unit cell are:
a=0.650 nm, b=0.663 nm, c=2.078 nm, α=90, β=99.5, γ=90
I have created 6 replicas along x axis, 8 along y axis and 3 along z axis. That gives me:
6a=3.9, 8b=5.304, 3c=6.234
How can I write correctly these coordinates to a gro file?
In a post I read that the box vector in a gro file follow the sequence of:
ax by cz ay az bx bz cx cy
If that’s true, then in my case:
3.9 5.304
sin(γ) 6.234 0 0 5.304*cos(γ) 0 0 0
Is that correct?
Thank you in advance.


To build a triclinic box with desired vectors and angles, you can use gmx editconf together with options -box -angle see gmx editconf — GROMACS 2021 documentation

Anyway if it helps here, you can find the format of the gro file File formats — GROMACS 2021.1 documentation

Best regards

I gave it a try and that seems to work,
Thank you.