Hi Everyone,

I have Three quick questions about the trg file created with gulp in a ascii format.

First, where does the derivative come from in the .trg file?

I dont think it is the derivative of the velocity on each atom because I keep some of them fixed in my MD run and they still have a non zero value for the derivative.

Is it the forces on each atom? Which to me does not make sense either because they should be positive (for the molecule I kept fixed) but I have half of the values positive and half negative.

Also, the goal for me is to extract the forces on each atom at the end of the MD run. Does anyone know how to do this WITHOUT a visualiser?

Thank you in advance for yourt time.

JJ