Hoping to fix orientation when using "fix pour" with the "mol" and "rigid" keywords

Hello everyone,

I noticed in the documentation for the “fix pour” command that when inserting molecules, “they are also oriented randomly”. I believe this is responsible for some issues I’m having. Is there any workaround to fix the orientation (or at least one component of the orientation) when using fix pour with rigid molecules?

To give some context, the simulations I am running involve a quasi-two-dimensional hopper and I am using “fix pour” with the “mol” and “rigid” keywords. These rigid structures often clip through the walls I have set up when they are inserted as they are oriented in ways incompatible with the geometry of the hopper.

One possible solution would likely be to pour from outside of the hopper. However, I’d like to avoid this if possible as it seems it would be very inefficient and slow.

Thank you for your time,

If you want to change the orientation of the inserted
molecules, you’ll need to go into the source code
for fix pour and remove the randomness. Generally
a “pour” is meant to be random, so that is what
the code does. You should also be using a small
enough region for pouring that the orientation will
not matter, with respect to the simulation box
boundaries. I.e. there will be no overlaps with
the walls.