Dear LAMMPS users and developers,

I want to obtain the specific heat by calculating dH/dT under NPT ensemble.

I do not know how to calculate dH/dT in a proper way. I try to use finite difference to approximate derivative. However, I got a negative value no matter the difference formulas used including forward, backward and central difference.

I convert eV to J/mol as: enthalpy(in eV)*1.602176634e-19/(natoms/6.02214076e23)

The H-T and dH/dT-T relation in my simulation have been uploaded. The simulation temperature is 2000K. Could someone please give me some suggestions? Thanks for any help one can give.