I am slowly learning more about C and it isn't quite as daunting as I thought it would be. I've now added a subtracted Gay-Berne pair interaction for bound Gay-Berne pairs and I'm wondering how one goes about adding these modifications to the development area. In addition it is my impression that the Gay-Berne potential wasn't fully implemented. Basically there was no way to enter or modify the default rotational inertias I_xx, I_yy and I_zz from their default values of "1". This gave some interesting results. The particle properties have been modified to incorporate a rotational inertia and I've made some modest "fixes" to the Gay-Berne subroutines. I've tried hard to follow syntax of existing particle parameters so that reading, writing and interprocess communication is done according to the established protocol. There is still more to do but the current subroutines are in reasonable shape.
Problem with the simulation: I can now model bonded GB particles but there is a strange behavior which I cannot figure out how to eliminate. I create a harmonic potential between GB particles and, as the simulation runs, the interparticle distance for at least one pair increases without end until the bond broken error flag 083 terminates the program execution. I can monitor the force vector and, when I do, I note that the force becomes very large as well. For some reason the NPT integrator doesn't seem to be doing the right thing. Increasing the spring constant doesn't help. Any thoughts/suggestions would be very welcome.
Mapping of Gay-Berne particles: I would like to use the interactive imd subroutine to allow me to watch the simulation in real time. Each GB particle represents a benzene type structure and it is relatively easy to use the GB particle position and quaternion to reconstitute the fine grain picture. To integrate this into Espresso it would be nice to have a "sub-particle" mapping which would generate the fine grain picture for the vmd program. If anyone has a good idea as to how this could be most easily implemented I would like to hear their suggestions. I've started to clone the particle_data.h and particle_date.c subroutines for generating subparticles but I think this is really a difficult task.
Thanks for any assistance,
Michael
--------------------------- Dept. of Physics University of Wisconsin --------------------------