The answer is very simple: E is the internal energy per atom in the system,

and F = E-TS is the free energy per atom. You can easily verify that by using

the number atoms per mole (Avogadro's number 6.022 x 10^23) and the conversion between eV and Joule: 1 eV = 1.60218 x 10^(-19) Joule.

Thank you. This table is a file of the output of phonons DOS for C3N4 compound?

Well, in that case, the unit is not an atom but a C3N4 molecule and Avogadro's number defines the number of these molecules in a mole of the compound. The relations I mentioned in my earlier answer remain the same

OK. Thank you. Now it's clear.

Hi Rachid Baghdad

In the output file of the phonon density calculation, the values given in the attached table correspond to thermodynamic properties at different temperatures. Specifically:

• E (eV): This represents the internal energy at the given temperature, which includes the zero-point energy and the thermal energy contributions from the phonons.
• F (eV): This represents the Helmholtz free energy at the given temperature, which is calculated as: F=E−TSF = E - TSF=E−TSwhere TTT is the temperature in Kelvin, and SSS is the entropy in J/mol/K.

At 298 K, the values are:

• E=3.541961E = 3.541961E=3.541961 eV
• F=3.298459F = 3.298459F=3.298459 eV

These values indicate how the vibrational energy and free energy of the system change with temperature.

Thank you for your response.

What is the meaning in the output file of the optimized cell:

Pseudo atomic calculation performed for C 2s2 2p2

Converged in 19 iterations to a total energy of -145.7159 eV

Pseudo atomic calculation performed for N 2s2 2p3

Converged in 23 iterations to a total energy of -261.3616 eV

Is these energies of free C and N atoms or their energies in the cell?