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Lattice thermal conductivity (κL) is a crucial characteristic of crystalline solids with significant implications for thermal management, energy conversion, and thermal barrier coating. The advancement of computational tools based on density functional theory (DFT) has enabled the effective utilization of phonon quasi-particle-based approaches to unravel the underlying physics of various crystalline systems. While the higher order of anharmonicity is commonly used for explaining extraordinary heat transfer behaviors in crystals, the impact of exchange-correlation (XC) functionals in DFT on describing anharmonicity has been largely overlooked. The XC functional is essential for determining the accuracy of DFT in describing interactions among electrons/ions in solids and molecules. However, most XC functionals in solid-state physics are primarily focused on computing the properties that only require small atomic displacements from the equilibrium (within the harmonic approximation), such as harmonic phonons and elastic constants, while anharmonicity involves larger atomic displacements. Therefore, it is more challenging for XC functionals to accurately describe atomic interactions at the anharmonicity level. In this study, we systematically investigate the room-temperature κL of 16 binary compounds with rocksalt and zincblende structures using var- ious XC functionals such as local density approximation (LDA), Perdew-Burke-Ernzerhof (PBE), revised PBE for solid and surface (PBEsol), optimized B86b functional (optB86b), revised Tao-Perdew-Staroverov-Scuseria (revTPSS), strongly constrained and appropriately normed functional (SCAN), regularized SCAN (rSCAN) and regularized-restored SCAN (r2SCAN) in combination with different perturbation orders, including phonon within harmonic approximation (HA) plus three- phonon scattering (HA+3ph), phonon calculated using self-consistent phonon theory (SCPH) plus three-phonon scattering (SCPH+3ph), and SCPH phonon plus three- and four-phonon scattering (SCPH+3,4ph). Our results show that the XC functional exhibits strong entanglement with perturbation order and the mean relative absolute error (MRAE) of the computed κL is strongly influenced by both the XC functional and perturbation order, leading to error cancellation or amplification. The minimal (maximal) MRAE is achieved with revTPSS (rSCAN) at the HA+3ph level, SCAN (r2SCAN) at the SCPH+3ph level, and PBEsol (rSCAN) at the SCPH+3,4ph level. Among these functionals, PBEsol exhibits the highest accuracy at the highest perturbation order. The SCAN- related functionals demonstrate moderate accuracy but are suffer from numerical instability and high computational costs. Furthermore, the different impacts of quartic anharmonicity on κL in rocksalt and zincblende structures are identified by all XC functionals, attributed to the distinct lattice anharmonicity in these two structures. These findings serve as a valuable reference for selecting appropriate functionals for describing anharmonic phonons and offer insights into high-order force constant calculations that could facilitate the development of more accurate XC functionals for solid materials. 

Rhenium chalcohalide cluster compounds are a photoluminescent family of mixed-anion chalcohalide cluster materials. Here we report the new material Rb6Re6S8I8, which crystallizes in the cubic space group Fm m and contains isolated [Re6S8I6]4− clusters. Rb6Re6S8I8 has a band gap of 2.06(5) eV and an ionization energy of 5.51(3) eV, and exhibits broad photoluminescence (PL) ranging from 1.01 eV to 2.12 eV. The room-temperature PL exhibits a PL quantum yield of 42.7% and a PL lifetime of 77 μs (99 μs at 77 K). Rb6Re6S8I8 is found to be soluble in multiple polar solvents including N,N-dimethylformamide, which enables solution processing of the material into films with thickness under 150 nm. Light-emitting diodes based on films of Rb6Re6S8I8 were fabricated, demonstrating the potential for this family of materials in optoelectronic devices. 

Abstract The development of efficient thermal energy management devices such as thermoelectrics and barrier coatings often relies on compounds having low lattice thermal conductivity (κ_l). Here, we present the computational discovery of a large family of 628 thermodynamically stable quaternary chalcogenides, AMM′Q₃(A = alkali/alkaline earth/post-transition metals; M/M′ = transition metals, lanthanides; Q = chalcogens) using high-throughput density functional theory (DFT) calculations. We validate the presence of lowκ_lin these materials by calculatingκ_lof several predicted stable compounds using the Peierls–Boltzmann transport equation. Our analysis reveals that the lowκ_loriginates from the presence of either a strong lattice anharmonicity that enhances the phonon-scatterings or rattler cations that lead to multiple scattering channels in their crystal structures. Our thermoelectric calculations indicate that some of the predicted semiconductors may possess high energy conversion efficiency with their figure-of-merits exceeding 1 near 600 K. Our predictions suggest experimental research opportunities in the synthesis and characterization of these stable, lowκ_lcompounds. 

Subchalcogenides are uncommon, and their chemical bonding results from an interplay between metal–metal and metal–chalcogenide interactions. Herein, we present Ir 6 In 32 S 21 , a novel semiconducting subchalcogenide compound that crystallizes in a new structure type in the polar P 31 m space group, with unit cell parameters a = 13.9378(12) Å, c = 8.2316(8) Å, α = β = 90°, γ = 120°. The compound has a large band gap of 1.48(2) eV, and photoemission and Kelvin probe measurements corroborate this semiconducting behavior with a valence band maximum (VBM) of −4.95(5) eV, conduction band minimum of −3.47(5) eV, and a photoresponse shift of the Fermi level by ∼0.2 eV in the presence of white light. X-ray absorption spectroscopy shows absorption edges for In and Ir do not indicate clear oxidation states, suggesting that the numerous coordination environments of Ir 6 In 32 S 21 make such assignments ambiguous. Electronic structure calculations confirm the semiconducting character with a nearly direct band gap, and electron localization function (ELF) analysis suggests that the origin of the gap is the result of electron transfer from the In atoms to the S 3p and Ir 5d orbitals. DFT calculations indicate that the average hole effective masses near the VBM (1.19 m e ) are substantially smaller than the average electron masses near the CBM (2.51 m e ), an unusual feature for most semiconductors. The crystal and electronic structure of Ir 6 In 32 S 21 , along with spectroscopic data, suggest that it is neither a true intermetallic nor a classical semiconductor, but somewhere in between those two extremes.