Page 1 of 1

How to maintain constant density of water with NPT ensemble?

Posted: Sat Jun 10, 2023 3:40 am
by jun_yin2
Dear all,

I have constructed a solid-liquid interface model with water as the liquid phase. During the AIMD simulation, I used the NPT ensemble. However, I noticed that under the NPT ensemble, the entire model's lattice changes significantly, especially the volume of the water in the upper liquid phase, which leads to an inconsistent density. I would like to know if there is a way to maintain a constant density of 1 g/cm3 for the water box while using the NPT ensemble?

Hope you can help me.

Re: How to maintain constant density of water with NPT ensemble?

Posted: Mon Jun 12, 2023 5:32 am
by marie-therese.huebsch
Hi,

In principle, it is not surprising the volume changes in an NpT ensemble. Can you specify what you mean by inconsistent density? Often it is hard to find a suitable value for LANGEVIN_GAMMA_L and PMASS. If they are too large, the simulation time becomes very long; if they are too small, the system can blow up (meaning that there are large fluctuations in pressure and volume).

To help further, I would need to see the input and main output as described in the forum guidelines.

Marie-Therese