About the reference state of Enthalpy

“thermo_style” command could output the Enthalpy of the simulated system, any one can tell me what’s the reference state of Enthaly?


Li dongdong

Graduate Student

Qinghai Institute of Salt Lakes, Chinese Academy of Sciences.

Xinning Road 18#, Xining, Qinghai, Peoples Republic of China.

Aidan probably knows off the top of his head.


The enthalpy is actually computed as:

      enthalpy = etotal + press*vol

or in the code:

  dvalue = etmp + ptmp*vtmp/(force->nktv2p);

where etotal, volume and pressure are all instantaneous values. This
equation is analogous to the thermodynamic equation:

H = U + pV

This definition does not use a reference state (state where H is
identically zero). However, for a system at zero temperature (all
velocities = 0) and zero pressure (dEpot/dV = 0), the enthalpy will be
equal to Epot, where Epot is the potential energy of the interatomic
potential. So I suppose you could use that as the reference state. There
are other choices for enthalpy that can be made that may be more
appropriate for specific applications.