Physics:Isoenthalpic–isobaric ensemble
Statistical mechanics |
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The isoenthalpic-isobaric ensemble (constant enthalpy and constant pressure ensemble) is a statistical mechanical ensemble that maintains constant enthalpy [math]\displaystyle{ H \, }[/math] and constant pressure [math]\displaystyle{ P \, }[/math] applied. It is also called the [math]\displaystyle{ NPH }[/math]-ensemble, where the number of particles [math]\displaystyle{ N \, }[/math] 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 [math]\displaystyle{ V \, }[/math] of a system to which the coordinates of all particles are relative. The volume [math]\displaystyle{ V \, }[/math] becomes a dynamical variable with potential energy and kinetic energy given by [math]\displaystyle{ PV \, }[/math].[2] The enthalpy [math]\displaystyle{ H=E+PV \, }[/math] is a conserved quantity.[3] Using isoenthalpic-isobaric ensemble of Lennard-Jones fluid, it was shown [4] that the Joule–Thomson coefficient and inversion curve can be computed directly from a single molecular dynamics simulation. A complete vapor-compression refrigeration cycle and a vapor–liquid coexistence curve, as well as a reasonable estimate of the supercritical point can be also simulated from this approach. NPH simulation can be carried out using GROMACS and LAMMPS.
References
- ↑ Andersen, H. C. Journal of Chemical Physics 72, 2384-2393 (1980).
- ↑ Hwee, Chiang Soo. "Mechanical behavior of peptides in living systems using molecular dynamics."
- ↑ Other Statistical Ensembles[|permanent dead link|dead link}}]
- ↑ Kioupis, L. I.; Arya, G.; Maginn E. I. Pressure-enthalpy driven molecular dynamics for thermodynamic property calculation II: applications. Fluid Phase Equilibria 200, 93–110 (2002).[1]
Original source: https://en.wikipedia.org/wiki/Isoenthalpic–isobaric ensemble.
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