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# Isoenthalpic–isobaric ensemble

Statistical mechanics
Microcanonical ensemble
Canonical ensemble
Grand canonical ensemble
Isothermal–isobaric ensemble
Isoenthalpic–isobaric ensemble
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The isoenthalpic-isobaric ensemble (constant enthalpy and constant pressure ensemble) is a statistical mechanical ensemble that maintains constant enthalpy $H \,$ and constant pressure $P \,$ applied. It is also called the NpH-ensemble, where the number of particles $N \,$ is also kept as a constant. It was developed by physicist H. C. Andersen in 1980.[1] The ensemble adds another degree of freedom, which represents the variable volume $V \,$ of a system to which the coordinates of all particles are relative. The volume $V \,$ becomes a dynamical variable with potential energy and kinetic energy given by $PV \,$.[2]. The enthalpy $H=E+PV \,$ is a conserved quantity.[3]

## References

1. ^ Andersen, H. C. Journal of Chemical Physics 72, 2384-2393 (1980).
2. ^ Hwee, Chiang Soo. "Mechanical behavior of peptides in living systems using molecular dynamics."
3. ^ Other Statistical Ensembles