Hi every one,

Using the Amorpous cell module I built a cell with 100 molecules of water (14,4x14,4x14,4), with Compass forcefield, Qeq charge equilibration, Ewald electrostatic and Atom based VdW, then with forcite I've done a geometry optimization.

In order to estimate the viscosity of water (just for test purpose) I used the Forcite shear job, and COMPASS as a forcefield, for the dynamic parameter I used a time step of 1fs with the NVT ensemble and with T=298K, obviously, the shear direction does not affect the results because my system is isentropic, so I used the software default value (B (BC)), However, the shear rate should be chosen carefully to get accurate results, of course the average is calculated after equilibration of the system, so here is a table with some of my results:

As you can see, the viscosity is too low compared to experimental results (0.896 cP at 298K).

In the other hand, I tried to change the target temperature, but strangely, there is no considerable change in the values!

And I don't know how to explain this...

Thank you very much

JARRAY