From Electronic Structure to Thermodynamics of Actinide-Based Alloys

Turchi, P. E. A.; Söderlind, Per; Landa, A.

doi:10.1007/s11837-014-0882-6

Cited by 9 publications

(4 citation statements)

References 69 publications

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“…Another challenging aspect of these heavy materials is the need to account for all relativistic effects, including spin-orbit interaction. Previous DFT studies on the bcc and fcc phases for actinide alloys have revealed that a fully-relativistic treatment is necessary for an accurate determination of the energetics of all Pu-based alloys [20,32,33,34]. Because relativistic effects cannot be ignored, the exact muffin-tin orbital (EMTO) electronic-structure method has been utilized here that applies a fully relativistic (FR) Green's function technique (based on the improved screened Korringa-Kohn-Rostoker method).…”

Section: Ab Initio Methods and Resultsmentioning

confidence: 99%

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The Pu–U–Am system: An ab initio informed CALPHAD thermodynamic study

Perron

Turchi

Landa

et al. 2015

Journal of Nuclear Materials

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Phase diagram and thermodynamic properties of the Am-U system, that are experimentally unknown, are calculated using the CALPHAD method with input from ab initio electronic-structure calculations for the fcc and bcc phases. A strong tendency toward phase separation across the whole composition range is predicted. In addition, ab initio informed Pu-U and Am-Pu thermodynamic assessments are combined to build a Pu-U-Am thermodynamic database. Regarding the Pu-rich corner of the ternary system, predictions indicate that Am acts as a powerful δ-Pu (fcc) stabilizer. In the U-rich corner, similar predictions are made but to a lesser extent. In both cases, the bcc phase is destabilized and the fcc phase is enhanced. Finally, results and methodology are discussed and compared with previous assessments and guidelines are provided for further experimental studies.

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Section: Ab Initio Methods and Resultsmentioning

confidence: 99%

“…(a) Heats of formation (symbols, in kJ/mol) of the bcc phase for the Am-U[34], Am-Np[34], Am-Pu[33] and Pu-U[32] alloys and of the fcc phase for Am-U (present study) and Am-Pu [20] systems at T = 0 K, based on the FR-EMTO-CPA method. (b) Metastable miscibility gaps calculated using Eq.…”

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confidence: 99%

The Pu–U–Am system: An ab initio informed CALPHAD thermodynamic study

Perron

Turchi

Landa

et al. 2015

Journal of Nuclear Materials

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“…4 Liquidus and solidus curves from Bochvar et al [3] , Marples [4] , Taylor [15] , Maeda et al [30] , and Leibowitz et al [31] . Redrawn from Maeda et al [30] and presented by Turchi and Perron in [40] , reproduced here with permission from ANS the composition variation of the heat of formation of the bcc phase (e-Pu, b-Zr) of Pu-Zr obtained from these three assessments [1,32,33] with the one from ab initio electronic structure calculations performed with the fully-relativistic (FR) exact muffin-tin orbital (EMTO) and coherent potential approximation (CPA) methods (FR-EMTO-CPA) at T = 0 K. [34,35] As observed in Fig. 7, there is a common major disagreement: The ab initio results show a change of sign around 46 at.% Zr with a tendency toward phase separation for plutonium-rich alloys and a tendency toward phase formation for zirconium-rich alloys, although the overall magnitude of the heat of formation is small, in contrast with the three thermodynamic assessments, which clearly indicate a tendency toward phase separation in the entire range of alloy composition and much higher values for the heat of formation.…”

Section: Thermodynamic Modelingmentioning

confidence: 99%

Experimental and Modeling Review of the Plutonium-Zirconium (Pu-Zr) System: Lost in Translation and Over Time?

Perron

Turchi

2020

J. Phase Equilib. Diffus.

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This article presents a review of the phase equilibria of the Pu-Zr system and discusses the contradictory reports on the experimental phase diagram and misinterpretations that have led to confusion over time. In addition, a review of the few Pu-Zr CALculation of PHAse Diagrams (CALPHAD) assessments is presented with emphasis on the heat of formation of the bcc phase, highlighting a disagreement between CALPHAD and ab initio calculations. Based on the information gathered in this study, a critical re-assessment of the Pu-Zr system involving the f (Pu 28 Zr), h (Pu 4 Zr), kinetically hindered j (PuZr 2 ), and once observed i phases is called for.This article is an invited paper selected from presentations at ''PSDK XIV: Phase Stability and Diffusion Kinetics-Gibbs: Phase Equilibria, Diffusion and Materials Design'' held during MS&T'19, September 29-October 3, 2019, in Portland, Oregon. The special sessions were dedicated to honor Dr. Patrice Turchi, recipient of the ASM International 2019 J. Willard Gibbs Phase Equilibria Award ''for outstanding and pioneering contributions in the application of first-principles, quantum-mechanical calculations to the modeling of phase equilibria and thermodynamic behavior of alloys.'' It has been expanded from its original presentation.

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“…Despite the demonstrable value of CSP for many classes of materials [21][22][23][24][25][26][27][28][29][30][31][32], and the continuing progress evidenced by a series of blind tests [33][34][35][36][37][38], the success of CSP for molecular crystals has been limited by the inability to routinely predict the relative stability of competing candidate structures [38]. This is largely because the methods used for stability rankings typically ignore or approximate the subtle interplay of several effects, such as intricate inter-molecular interactions [39], the (quantum) statistical mechanics of the nuclei [40] and the unit cell [41], and thermal expansion [42], thereby incurring errors larger than the free energy differences of interest.…”

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A complete description of thermodynamic stabilities of molecular crystals

Kapil,

Engel

2021

Preprint

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Accurate prediction of the stability of molecular crystals is a longstanding challenge, as often minuscule free energy differences between polymorphs are sensitively affected by the description of electronic structure, the statistical mechanics of the nuclei and the cell, and thermal expansion. The importance of these effects has been individually established, but rigorous free energy calculations, which simultaneously account for all terms, have been prevented by prohibitive computational costs.Here we reproduce the experimental stabilities of polymorphs of three prototypical compoundsbenzene, glycine, and succinic acid -by computing rigorous ab initio Gibbs free energies, at a fraction of the cost of conventional harmonic approximations. This is achieved by a bottom-up approach, which involves generating machine-learning potentials to calculate surrogate free energies and subsequently calculating true ab initio free energies using inexpensive free energy perturbations. Accounting for all relevant physical effects is no longer a daunting task and provides the foundation for reliable structure predictions for more complex systems of industrial importance.

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From Electronic Structure to Thermodynamics of Actinide-Based Alloys

Cited by 9 publications

References 69 publications

The Pu–U–Am system: An ab initio informed CALPHAD thermodynamic study

The Pu–U–Am system: An ab initio informed CALPHAD thermodynamic study

Experimental and Modeling Review of the Plutonium-Zirconium (Pu-Zr) System: Lost in Translation and Over Time?

A complete description of thermodynamic stabilities of molecular crystals

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