Dear LAMMPS users ,
I have a question about fix nph command :
I use this ensemble for TIP4P water molecule for getting instantaneous enthalpy
HNPH = etotal (t) + P * V (t)
this is a part of my input file :
timestep {dt}
fix nph all nph iso {pset} {pset} 1000
variable HNPH equal etotal+{pset}*vol/atoms
fix 2 all ave/time 100 10 1000 c_thermo_temp c_thermo_press v_HNPH file ave.out
run 100000
when I map out average temperature with respect to HNHP It shows just fluctuation of HNHP around a special amount .
This figure has to show stable branch ( positive slop ) for liquid and gas and also unstable branch with negative slop .
Hope someone could give me an advice.
Best,
saeed.