AMBER: amber 9 - output of forces

From: Eric Shamay <>
Date: Fri, 23 Mar 2007 16:00:39 -0700

After searching for a few days through the mail archive, I still haven't
found any concrete answers regarding the modification of the amber9 source
to output forces instead of velocities. I've done some work through the
sander source and come up with the following:

Please correct this, as my knowledge of fortran is rather limited.

in dynlib.f:
This file defines the 'corpac' routine, which as far as I can tell does the
actual output to the various files. The first parameter given to this
routine is an array: either the coordinates or velocities. If we were to
give, instead, the force array, this routine would print out those values.
The only modification I thought of in this file was to change the output
format if desired. I want better precision, so I modified lines 41-45:

      if (three_digit_fractional_part) then
         write(nf,'(10f8.3)') (r(j),j=istart,n)
         write(nf,'(10f8.2)') (r(j),j=istart,n)
      end if

such that the format given will have 7 digits after the decimal point.

in runmd.f
line 2092: if (ivdump) call corpac(v,1,nrx,MDVEL_UNIT,loutfm)
was commented out. I've replaced this line with

if (ivdump) call corpac(f,1,nrx,MDVEL_UNIT,loutfm)

the only change being that I'm feeding corpac my force array 'f' instead of
the velocities 'v'

Does this all make sense? Am I missing something fundamental that makes this
all wrong? Please respond if you've tinkered with the source at all.

~Eric Shamay
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Received on Sun Mar 25 2007 - 06:07:51 PDT
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