[gmx-users] Which variable represents the potential energy ?

[masakatsu-ito at aist.go.jp]

Hi,

I am trying to make another implementation of replica exchange method
(REM) which calls gromacs code for calculating potential energies.
However, my program still does not work because the potential energy
at each step becomes zero.

I assumed that do_force() function calculates the potential energy,
and ener[F_EPOT] variable in this function represents the potential
energy. But I found that ener[F_EPOT] is zero after calling do_force()
in both my REM program and mdrun.

So could please anybody tell me which argument of do_force()
represents the potential energy ? This function has a argument list
like

  FILE *log, t_commrec *cr, t_commrec *mcr,
  t_parm *parm,t_nsborder *nsb,tensor vir_part,tensor pme_vir,
  int step,t_nrnb *nrnb,t_topology *top,t_groups *grps,
  rvec x[],rvec v[],rvec f[],rvec buf[],
  t_mdatoms *mdatoms,real ener[],t_fcdata *fcd,bool bVerbose,
  real lambda,t_graph *graph,
  bool bNS,bool bNBFonly,t_forcerec *fr, rvec mu_tot,
  bool bGatherOnly
.

Or should I call another function to get the potential energy?

Thanks a lot in advance.
Masakatsu

Masakatsu Ito , Ph.D

Grid Technology Research Center
National Institute of Advanced Industrial Science and Technology
Tsukuba Central 2, Tsukuba, Ibaraki 305-8568 Japan
Phone : +81-29-861-5730  Fax : +81-29-861-5301
E-mail masakatsu-ito at aist.go.jp
URL http://met.sourceforge.net/