I am trying to minimize (cg) a slab of SPC/E water (p p f) so that the unit cell vectors remain fixed but only
the coordinates are optimized. At the moment whenever I optimize my system the cell vectors are changing.
Is there a way to optimize just the coordinates?.
I don’t understand the question completely. How can the coordinates be optimized if the unit cell is fixed? Do you want to optimize the atoms only along the unit vectors? If so, fix lineforce might help but I’m not sure.
Do you mean you don’t want the box size to change? If yes, you must have use a command called “fix box/relax” - just remove this command.