Biphasic system

Hi,
I am building a biphasic system consisting of ethylbenzene and water. Using the gmx insert-molecule i created a box of dimension 15 15 4, with 2754 ethylbenzene molecule the maximum that could fit the box. Then did energy minimization and NVT equilibration. During the NVT equilibration i am facing the issue, the entire structure gets deformed as shown in the attached figure.
EB-gro

Any help would be appreciated
Thanking you

Constant volume simulation means the box size can’t change. That is not a deformation, it is the liquid getting to it’s correct simulation density. Obviously the density of the liquid is higher than what you generated so some areas form a “vacuum”. Best solution is to run NPT for awhile, get the density stable then return to your NVT settings.