A new thermodynamic description of pure silicon from 0 K at 1 bar

Abstract

Third-generation Calphad models have been applied to describe the thermodynamic properties of pure crystalline and liquid/amorphous silicon. The extended Planck-Einstein model was used to evaluate the standard entropies at 298.15 K; the values for the amorphous phase were reported for the first time. A new approach was proposed for the evaluation of parameters for the two-state liquid model for pure silicon. In the majority of previous 3rd-generation CALPHAD assessments it was proposed to fix the enthalpy or entropy parameters of the ΔGdif equation, which could result in the inability of the model to describe the thermodynamics of the fusion of the pure elements. The alternative approach is to derive these parameters from the fixed fraction of translational (liquid-like) atoms at the fusion temperature and to compare the results with the heat capacity data. The new model representation of the liquid/amorphous phase allows us to obtain a better description of the experimental data for the isobaric heat capacity of the liquid phase.