A Third Generation Calphad Description of Pure Lithium

Area of Science:

• Thermodynamics
• Materials Science
• Computational Materials Science

Background:

• Existing thermodynamic databases for lithium require updates for comprehensive temperature range coverage.
• Accurate phase descriptions are crucial for materials modeling and simulation.

Purpose of the Study:

• To develop a third-generation CALPHAD (Calculation of Phase Diagrams) description for lithium.
• To extend the description of lithium phases down to 0 K.
• To improve the accuracy of thermodynamic modeling for lithium.

Main Methods:

• Analysis of existing experimental data.
• Application of nonlinear least squares in MATLAB.
• Expansion of the SGTE (Scientific Group Thermodata Europe) database for lithium.
• Utilizing the extended Debye model, two-state model, and extended Einstein model.

Main Results:

• A third-generation CALPHAD description for lithium covering all temperature ranges was established.
• Lithium phases (fcc, bcc, liquid) were described down to 0 K with improved accuracy.
• The low-temperature phase of lithium was confirmed as face-centered cubic (fcc).
• Accurate description of crystalline lithium's heat capacity was achieved.

Conclusions:

• The developed CALPHAD description significantly improves agreement with experimental data compared to previous assessments.
• This enhanced thermodynamic model provides a more reliable basis for predicting lithium behavior in various applications.
• The study highlights the importance of accurate thermodynamic data for materials development.