Interactive MD example files using the fix imd command

To run the demos, first start the LAMMPS simulation, during
initialization it will stop and wait for an IMD client to
connect. Then launch VMD on the same machine with the respective
script to connect and visualize the running simulation.  For example:

mpirun -np 4 lmp_linux -log none -in in.melt_imd &
vmd -e melt_imd-demo.vmd

When exiting VMD, the simulation will either continue or wait
for a new connection depending on whether the "nowait" flag was
activated or not.  To terminate the LAMMPS simulation, 
type "imd kill" into the VMD command line prompt.

To combine interactive MD with force feedback using a
Novint Falcon game controller, have a look at:
http://sites.google.com/site/akohlmey/software/vrpn-icms

Examples:

 melt: 
       an adapted version of the 3d-LJ melt example.
       the VMD visualization contains one highlighted
       atom to play with force application through a
       mouse: Open the Graphical Representations dialog,
       Double-click on the first VDW representation
       to disable it, click with the mouse on the blue
       atom and - while holding the mouse button down -
       drag the atom into some direction. A red arrow
       should appear indicating direction and magnitude
       of the force. Now double-click on the first VDW
       representation again to re-enable the rest of
       the atoms and watch the blue atom move.

bucky-plus-cnt:
       this is "the buckyball challenge". a demo that
       is very popular to demonstrate the use of IMD
       with force feedback. The system is a SWCNT with
       some atoms fixed in space and five C60 fullerenes
       in a reflecting wall box. The challenge is to
       push all five buckyballs into the nanotube and
       have them stay inside.

 deca-ala-solv:
       a solvated deca alanin helix. The mouse mode is
       preset to move residues instead of individual
       atoms. Disable the water rep and grab an atom
       from the peptide and drag it to apply forces.

 deca-ala:
       this is the same system as the previous, but 
       the fix is only applied to the peptide and thus
       the corresponding VMD script needs a different
       topology file with the matching number of atoms
       to visualize it and receive the IMD data.

In case of problems, contact <akohlmey@gmail.com>.
