Hello everyone!

I am working on polymeric composite now. I investigate the interaction between nanoclay and polymeric matrix. I've added polymeric matrix between two layers of MMT. For minimization, I have constrainted two layers of MMT, while the polymeric matrix is free. I should add that I used "fixed fractional positions" and also fixed a and b ( x and y directions) and alpha and betha and gama.

After a successful minimization run using Forcite, I want to perform a NPT run.  Now, I have a question. When I run the simulation cell under a NPT run using Forcite, inadition to c direction, the a and b directions also change while I had fixed it before. Could anyone help me to find its problem if there is?

Also, I should say that I use MS 4.3.

Regards,

M