CCS and Power Systems
Crosscutting Research - University Training and Research
Computational Studies of Physical Properties of Nb-Si Alloy
Performer: Tennessee State University
Project No: FE0003798
TSU has demonstrated the Gibbs free energy module for calculating temperature pressure dependent elastic constants on several systems including the Nb metal, Nb-Si alloys, and silicon carbide (SiC). For insulator SiC, the calculated temperature coefficients of elastic constants for both cubic and hexagonal SiC are in excellent agreement with the experimental data. For Nb, the calculated elastic constants at low temperature showed notable error. The error has been traced to insufficient k-space sampling and supercell size used in the phonon calculation. More accurate calculations are planned. TSU researchers have completed the calculations of Gibbs free energy, specific heats, thermal expansion coefficients, entropy, and elastic constants for all known crystal phases of the binary Nb-Si alloys and are currently working on thermodynamic databases for Nb-Si-Cr ternary systems for selected crystal phases. TSU is continuing to improve the post-processing codes for Gibbs free energy calculation, temperature and pressure dependent elastic constants calculation, and other thermodynamic properties. The draft temperature pressure dependent elastic constants of SiC have been completed and will be submitted for review soon. TSU is currently developing a flexible cluster variation method that will enable computation of the free energy and stress for disordered systems and refining the calculation of elastic constants based on free energies in proximity to the temperature-hydrostatic pressure surface of states.