********> bugfix.61
Author:   Carlos Simmerling
Date:     1/17/96

Programs: Sander, Gibbs

Severity: Moderate

Problem:  When the compiler does not automatically initialize 
          variables to 0, an uninitialized variable can cause
          center of mass motion to be removed when not requested.

Affects:  T3D, SGI, possibly other machines. 

          Only occurs when:

            1) uninitialized variables not set to 0 
            2) INIT = 4 or NTCM = 0 in input.
            3) One is periodicially resetting ALL the velocities in the
               system randomly. That is, only when NTT<0 and the necessary
               criteria have been met to force a rescaling. Removal of
               center of mass motion only occurs at the time the velocities
               are randomly reassigned.


Fix:  Make the following change to sander/runmd.f:
----------------------------------------------------------------------
*** OLD runmd.f
--- NEW runmd.f
***************
*** 123,128 ****
--- 123,129 ----
        peac = tauv0.gt.small .and. tauv.gt.small
        tauv = 20.455*tauv
        td = t
+       ntcmt = 0
        intcm = max(nstlim/10,ntpr)
        if (intcm .lt. 100) intcm = 100
        IZERO = 0
----------------------------------------------------------------------
Fix:  Make the following change to gibbs/giba.f:
----------------------------------------------------------------------
*** OLD giba.f
--- NEW giba.f
***************
*** 2272,2277 ****
--- 2272,2278 ----
  C NODERV...Logical flag set to .true. when free energy derivatives are *not*
  C          being calculated (normal FEP operation)
  C
+       ntcmt = 0
        DS(1) = 0.0D0
        DS(2) = 0.0D0
        DE(1) = 0.0D0
----------------------------------------------------------------------

Temporary workarounds: none

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