LAUSR

In connection to developing the third generation of Calphad databases a new thermodynamic description is presented for unary carbon. Models used in this work have more physical basis and are valid down to 0 K. The anisotropy in graphite, caused by weak Van der Waals inter-plane forces makes it impossible to fit the heat capacity data by a single Einstein temperature for modelling the harmonic vibration of the atoms. By using multiple Einstein temperatures this problem is solved and a good agreement with the experimental data at both low and other temperatures is achieved. Diamond is modeled using multiple Einstein temperatures due to its specific heat capacities at very low temperatures too, and the two-state model is used for modelling the liquid phase.