The CHARMM Interface
Introduction
The CHARMM interface allows energies and gradients to be taken
from the CHARMM package which runs as an independent executable.
Communication with ChemShell is via named pipes, using the CTCL
procedures written by Alex Turner.
In order to use the interface, it is necessary to prepare a CHARMM
script that will set up the system and define all parameters needed
to generate a correct energy and gradient. After running this
script under control of the charmm.preinit command,
CHARMM waits for each set of coordinates to be sent from ChemShell.
The command charmm.shutdown is used to close down
the charmm process.
charmm.preinit
Command Line Arguments
| Argument |
Argument type |
Mandatory |
Default |
To specify |
| coords |
Fragment tag
|
yes |
none |
The coordinates of the system (output) |
| charmm_script |
file |
yes |
none |
Control script for CHARMM |
| executable |
file |
no |
charmm |
Name of CHARMM executable |
charmm.energy etc
Since all control information is fed to CHARMM via the charmm script,
very few arguments will be fed to the energy and gradient evaluation
routines (contrast with the DL_POLY interface, where all control is
provided by arguments).
Clearly, when the charmm interface procedures are executed arguments
are used to control the input coordinates, and output energy and
gradient matrices following the conventions used by all
energy/gradient evaluators.
Examples
# start charmm
charmm.preinit charmm_script=test.charmm coords=charmm.c
# optimise
newopt function=copt : { theory=charmm coords=charmm.c }
# end charmm
charmm.shutdown
|
