[gmx-developers] calculating poteintial energy into do_md()

[francesco oteri]

Dear gromacs developers,
I am trying to implement in gromacs 4.5.5 a particular Hemiltonian Replica
Exchange tecnique.
Right now, at every exchange attempt in do_md, I figured out  how to access
at the potential
energy of replica A (=configuration A at temperature A) and B
(=configuration B at temperature B) and so on.

In my case, each replica has the same temperature, but there is a different
Hemiltonian equation for every replica.
The different Hemiltonian are obtained simply changing the force field
parameters in the input topology so I dont
need to modify anything in gromacs.

But at every exchange attempt I have to test if the configuration B can
exist in the state A so I need to calculate
its potential energy using the force field data of replica A.

I found that function sum_epot calculates the potential energy but I
suspect that it uses values calculated in
do_force since sum_epot is called by do_force_lowlevel in turn called by
do_force.



So my question is, should I call do_force in replica A with coordinates
from replica B reach my goal?

Thanks in advance,

Francesco
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