Implementation of the extended Einstein and two-state liquid models for thermodynamic description of pure SiO2 at 1 atm

Thermodynamic description of pure SiO2 at 1 atm was developed for the whole temperature range including the crystalline, supercooled liquid and amorphous phases. Thermodynamic properties of the crystalline phases were assessed using an extended Einstein model. The thermodynamic modelling was based on the critically assessed experimental heat capacity and enthalpy increment data and on the data on phase transitions. The Planck-Einstein approach was used to evaluate the heat capacity data and obtain a more accurate value for the standard entropy at 298.15 K for α-quartz, α-cristobalite and amorphous∖liquid phases. The value for the standard entropy for the amorphous phase obtained just from the assessment of heat capacity data and did not include non-zero residual entropy at 0 K. The liquid and amorphous phases were thermodynamically described as one phase using the two-state liquid model. It was shown that Gibbs energy expression for amorphous silicon dioxide could be evaluated without inclusion of non-zero entropy at 0 K. •Solid phases of SiO2 (α- and β-quartz and α- and β-cristobalite) were described from 0 K to 6000 K with extended Einstein model.•Amorphous/liquid phase of SiO2 was described with two-state liquid model from 0 K to 6000 K.•Values for the standard entropies at 298.15 K for the crystalline and liquid/amorphous phases were evaluated with the use of Planck-Einstein approach.•The thermodynamic properties of liquid/amorphous phase were described without the inclusion of residual entropy at 0 K.