I am working with an energetic material. using a classical forcefield how can I calculate isothermal compressibility by volume fluctuation formula, and coefficient of thermal expansion by the enthaply-volume fluctuation formula for a solid in LAMMPS?
I think there is no direct keyword to compute these thermodynamic properties in LAMMPS.
In NPT ensemble, you need to calculate volume fluctuation (for isothermal compressibility) and cross-correlations of enthalpy and volume (for thermal expansion coefficient). (see Allen and Tildesley, Computer Simulation of Liquids)
using thermo_style command, like
thermo_style custom step temp pe press vol enthalpy,
you will be able to print instantaneous values in log file during simulation. After that, a little bit of post-processing will be needed to get the desired property.
Rahul Sahu thank you very much for your answer. Can you tell me something about calculating heat capacity using volume fluctuation formula ?
Hi Rifat,
Constant-pressure heat capacity (Cp) can be calculated from instantaneous fluctuation of enthalpy.
The screenshot I have attached is from Allen and Tildesley, Computer Simulation of Liquids book.
How to find rdf through fortran code using the results of lammps simulation
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