Phonon Band Center: A Robust Descriptor to Capture Anharmonicity

Abstract

Understanding anharmonicity is crucial for designing materials with desired lattice thermal conductivity. Designing a material descriptor that effectively captures anharmonicity while being cost-effective remains a significant challenge. This work proposes a simple metric that helps explain the diversity in lattice thermal conductivity (kl) among materials by quantifying their anharmonic effects. This descriptor "phonon band center" (PBC) encapsulates the critical factors associated with the physics of phonon scattering, revealing a simple inverse relationship with the Gruneisen parameter, the response of phonons with changing volume, and strong correlation with lattice thermal conductivity. This metric has been established using the chalcopyrite class of materials and subsequently validated across various classes of materials using experimental kl. Our approach effectively differentiates materials based on PBC, thereby streamlining the identification of candidates with desirable kl.

Figures (10)

• Figure 1: (a) High throughput workflow, column-wise calculated electron localization function (ELF), variation of Gr$\ddot{u}$neisen parameter ($\gamma_{QH}$) as a function of frequency and lattice thermal conductivity ($\kappa$) for three representative compounds having (b) ultrahigh (BeSiAs$_{2}$), (c) medium (BeSnSb$_{2}$), and (d) ultralow (AgInSe$_{2}$) range of thermal conductivity.
• Figure 2: Phonon density of states (PDOS) plot of (a)-(d) representative compounds from group II-IV-V$_{2}$, and (e)-(h) representative compounds from group I-III-VI$_{2}$ chalcopyrites. The black dotted line indicates the position of the total phonon band center (PBC). Corresponding calculated PBC values for the compounds from (i) II-IV-V$_{2}$, and (j) I-III-VI$_{2}$ chalcopyrites, where the color bar represents the value of $\gamma_{300}$. Variation of $\gamma_{300}$ with calculated phonon band center for (k, m) entire frequency range, and (l, n) considering a cut-off frequency range of 3 THz.
• Figure 3: (a) Experimentally measured lattice thermal conductivity ($\kappa_l$) values of Bi$_{2}$Se$_{3}$, Bi$_{2}$Te$_{3}$, PbS, PbSe, PbTe, SnS, SnSe, AlAs, AlP, BAs, BP, BN, GaAs, GaN, and Si wu2023experimentalzhao2014ultralowshinde2006highsze2021physicskarim1993characterizationkang2018experimentalmorelli2006highjezowski2003thermalfournier2018straightforwardbessas2012latticepei2012electricalbanik2016origin at 300 K and corresponding calculated phonon band center (PBC) values calculated using first-principles. Contour plot showing the variation of PBC$_{c=3}$ as a function of average bond distance (B$_{D}$), where the color bars represent the magnitude of (a) $\nu_{g}$, and (b) $\gamma_{300}$.
• Figure S1: Phonon dispersions of chalcopyrties
• Figure S2: Phonon dispersions of chalcopyrties