Creeping rigid molecules

Dear all

In my model, a set of TIP4P waters are enclosed by organic molecules. In order to utilize GPU capability, I made TIP4P by my own by using fix rigid. The input file is attached.

rigid waters and organics are integrated by fix rigid/nvt/small and fix NVT, respectively.

Everything (pressure, temperature and energy) took typical values, however, the aggregate of water molecules gradually moves in a direction, -Z. I used molecule keyword in fix rigid, but I cannot figure out this result?


in.Water_Phenol (1.56 KB)