AMBER Archive (2008)

Subject: AMBER: Using AMBER forces

From: Steven Winfield (saw44_at_cam.ac.uk)
Date: Tue Jun 24 2008 - 10:44:41 CDT

Dear all,

Firstly, let me apologise to the masses for a rather developer-specific
question.

I'm involved in a project which uses AMBER (version 9) as a force
evaluator - my program uses a given prmtop file, writes the current
atomic coordinates in AMBER format, prepares an input file (which could
contain a qm atom list) and calls a modified version of sander which
writes the total energy and the forces to a file, which my program then
reads in.

The only modification I have made to sander is the following, placed in
the force subroutine in force.f, between "call trace_exit( 'force' )"
and "return":

   open(unit=50,file='sander_forces.dat',action='write')
   write(50,*) ene(1)
   write(50,*) f(1:3*natom)
   close(50)
   call mexit(0,0)

so sander never gets further than the first call to force(). Is there
any reason why this shouldn't give the expected results, even when using
QM/MM? In particular, I see in the runmd() subroutine that the first MD
step (where this first force() call occurs) is treated differently to
the others.

If there is a simpler way to accomplish this I would also like to know.

Many thanks,

Steve.
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