Abstract
Density functional theory using the Perdew-Burke-Ernzerhof functional and the small displacement method was used to calculate the quasiharmonic phonon density of states (DOS) for 69 ordered structures in the Mo-Ru substitutional alloy system to estimate the effect of vibrational contributions to the free energy of formation. These structures were used to determine interaction parameters in the cluster expansion approximation up to triplet sets to incorporate the vibrational contribution into the configurational energy of formation for the randomly mixed system. The free energies calculated using this approximation are shown to resolve lingering disagreement between reported theoretical and experimental results, and the stabilizing effect of vibrational entropy is observed to improve theoretical predictions of the Mo-Ru phase diagram.
Original language | English |
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Pages (from-to) | 969-976 |
Number of pages | 8 |
Journal | Journal of Alloys and Compounds |
Volume | 689 |
DOIs | |
State | Published - 2016 |
Externally published | Yes |
Funding
This work was funded by Pacific Northwest National Laboratory utilizing Laboratory Directed Research and Development (LDRD) funds with support from the Nuclear Process Science Initiative (NPSI) and was performed using PNNL Institutional Computing (PIC). Pacific Northwest National Laboratory is operated by Battelle Memorial Institute for the United States Department of Energy under contract DE-AC06-76RLO-1830 .
Keywords
- Nuclear reactor materials
- Phase diagrams
- Phonons
- Thermal expansion
- Thermodynamic modeling
- Transition metal alloys and compounds