The effect of lattice vibrations on substitutional alloy thermodynamics

By Axel van de Walle, Gerbrand Ceder. 2001

609 citations recorded by the source corpus.

A long-standing limitation of first-principles calculations of substitutional alloy phase diagrams is the difficulty in accounting for lattice vibrations. A survey of the theoretical and experimental literature seeking to quantify the effect of lattice vibrations on phase stability indicates that they can be significant. Typical vibrational entropy differences between phases are of the order of 0.1 to 0.2kB/atom, which is comparable to the typical values of configurational entropy differences in binary alloys (at most 0.693kB/atom). This article presents the basic formalism underlying ab initio phase diagram calculations, along with the generalization required to account for lattice vibrations. The authors review the various techniques allowing the theoretical calculation and the experimental determination of phonon dispersion curves and related thermodynamic quantities, such as vibrational entropy or free energy. A clear picture of the origin of vibrational entropy differences between phases in an alloy system is presented that goes beyond the traditional bond counting and volume change arguments. Vibrational entropy change can be attributed to the changes in chemical bond stiffness associated with the changes in bond length that take place during a phase transformation. This so-called “bond stiffness vs bond length” interpretation both summarizes the key phenomenon driving vibrational entropy changes and provides a practical tool to model them.

Subfields: Atmospheric Science, Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/5448c765eba3e1a941ab4015dc21d0eec7e0a9ba

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In Atmospheric Science

In Atomic and Molecular Physics, and Optics

In Materials Chemistry

Citations in the corpus

Computational understanding of Li-ion batteries (2016, background): “Although the magnitude of the vibrational entropy may be significant, its variations across phases of the same chemical species are typically small so that it does not much affect the relative phase stability.(72) In addition, electronic contributions to the configurational entropy due to the orderi”
Stacking fault energies of face-centered cubic concentrated solid solution alloys (2017, positive): “Since S config is equal for both fcc and hcp structure (the same concentration in both structures), this term has no effect on phase stability and consequently is ignored [36].”
Multicomponent multisublattice alloys, nonconfigurational entropy and other additions to the Alloy Theoretic Automated Toolkit (2009, positive): “-length scheme [17], which is implemented in the fitsvsl and svsl codes.”
Predicting the formation and stability of single phase high-entropy alloys (2016, background): “Although other contributions to entropy such as vibrational, electronic and magnetic moment randomness can be present, these entropic contributions are often similar in ordered, segregated and solution phases of the system [25, 26], and therefore cancel in comparison.”
A critical review of high entropy alloys and related concepts (2016, background): “For example, bonds between unlike atoms with a covalent component are often stiffer and shorter than bonds between like atoms, reducing vibrational entropy relative to pure elements [78].”