The Molecule/Put command writes the coordinates of a molecule or assembly to a file. The file is given the extension .car. InsightII is a multi-purpose program that can write files for study using classical simulations (DISCOVER is the name of the Molecular Dynamics module) or a DFT calculations using DMol3. Since MD simulations require the assignment of a classical force field InsightII requires the definition of a force field before a file can be written even if the calculation is not a classical MD simulation.

What is worse is that if the force field parameters for a particular atom are not present then InsightII will simply refuse to write the file in some cases. This can always be circumvented. To assign parameters to any molecule use the following steps.

Choose the FF (force field) icon on the left of the InsightII window.

Select the ESFF force field (esff.frc) using the force field menu (in FF). Then assign the potential types and charges for the molecule using the potentials menu (in FF). Once this procedure has been completed you can write the file using the Molecule/Put command.