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We argue that the spatial discretization of the strongly nonlinear Lefever–Lejeune partial differential equation defines a nonlinear lattice that is physically relevant in the context of the nonlinear physics of ecosystems, modelling the dynamics of vegetation densities in dry lands. We study the system in the lattice ℤ2$$ {\mathrm{\mathbb{Z}}}^2 $$, which is especially relevant because of its natural dimension for the emergence of pattern formation. Theoretical results identify parametric regimes for the system that distinguish between extinction and potential convergence to nontrivial states. Importantly, we analytically identify conditions for Turing instability, detecting thresholds on the discretization parameter for the manifestation of this mechanism. Numerical simulations reveal the sharpness of the analytical conditions for instability and illustrate the rich potential for pattern formation even in the strongly discrete regime, emphasizing the importance of the interplay between higher dimensionality and discreteness. [ABSTRACT FROM AUTHOR]

We argue that the spatial discretization of the strongly nonlinear Lefever–Lejeune partial differential equation defines a nonlinear lattice that is physically relevant in the context of the nonlinear physics of ecosystems, modelling the dynamics of vegetation densities in dry lands. We study the system in the lattice ℤ2$$ {\mathrm{\mathbb{Z}}}^2 $$, which is especially relevant because of its natural dimension for the emergence of pattern formation. Theoretical results identify parametric regimes for the system that distinguish between extinction and potential convergence to nontrivial states. Importantly, we analytically identify conditions for Turing instability, detecting thresholds on the discretization parameter for the manifestation of this mechanism. Numerical simulations reveal the sharpness of the analytical conditions for instability and illustrate the rich potential for pattern formation even in the strongly discrete regime, emphasizing the importance of the interplay between higher dimensionality and discreteness. [ABSTRACT FROM AUTHOR]

We employ advanced first principles methodology, merging self‐consistent phonon theory and the Boltzmann transport equation, to comprehensively explore the thermal transport and thermoelectric properties of KCdAs. Notably, the study accounts for the impact of quartic anharmonicity on phonon group velocities in the pursuit of lattice thermal conductivity and investigates 3ph and 4ph scattering processes on phonon lifetimes. Through various methodologies, including examining atomic vibrational modes and analyzing 3ph and 4ph scattering processes, the article unveils microphysical mechanisms contributing to the low κL within KCdAs. Key features include significant anisotropy in Cd atoms, pronounced anharmonicity in K atoms, and relative vibrations in non‐equivalent As atomic layers. Cd atoms, situated between As layers, exhibit rattling modes and strong lattice anharmonicity, contributing to the observed low κL. Remarkably flat bands near the valence band maximum translate into high PF, aligning with ultralow κL for exceptional thermoelectric performance. Under optimal temperature and carrier concentration doping, outstanding ZT values are achieved: 4.25 (a(b)‐axis, p‐type, 3 × 1019 cm−3, 500 K), 0.90 (c‐axis, p‐type, 5 × 1020 cm−3, 700 K), 1.61 (a(b)‐axis, n‐type, 2 × 1018 cm−3, 700 K), and 3.06 (c‐axis, n‐type, 9 × 1017 cm−3, 700 K). [ABSTRACT FROM AUTHOR]

In this study, advanced first‐principles calculations combined with self‐consistent phonon theory and the Boltzmann transport equation are used to assess the thermoelectric properties of novel Full–Heusler materials X2YTe (X = Na, K, Rb, Cs; Y = Zn, Cd, Hg). These materials exhibit low formation energies, facilitating synthesis under standard conditions. This analysis showed that lattice anharmonicity increases with the atomic mass of X and decreases with the atomic mass of Y due to the rattling effect of Y atoms. Significant rattling effects are identified, prompting the inclusion of higher‐order anharmonic effects. By renormalizing the phonon spectrum and accounting for three‐phonon and four‐phonon scattering, the mechanisms behind the low lattice thermal conductivity in these compounds is uncovered. The combination of low lattice thermal conductivity and high power factors resulted in remarkable thermoelectric figure of merit values at optimal doping concentrations and temperatures. Notably, except for Na2ZnTe and Na2HgTe, all other materials surpassed the long‐standing figure of merit record of less than 3, with Rb2ZnTe achieving a figure of merit of 8.11 at 700 K with an n‐type doping concentration of 2 × 1019. The inclusion of spin‐orbit coupling led to less than a 10% reduction in the thermoelectric figure of merit, underscoring the superior thermoelectric performance of these materials. [ABSTRACT FROM AUTHOR]

Spin‐crossover (SCO) complexes have drawn significant attention for the possibility to photoswitch their electronic spin state on a sub‐picosecond timescale at the molecular level. However, the multi‐step mechanism of laser‐pulse‐induced switching in solid state is not yet fully understood. Here, time‐resolved synchrotron X‐ray diffraction is used to follow the dynamics of the crystal lattice in response to a picosecond laser excitation in nanometric thin films of the SCO complex [Fe(HB(1,2,4‐triazol‐1‐yl)3)2]. The observed structural dynamics unambiguously reveal a lattice expansion on the 100 picosecond timescale, which is temporally decoupled both from the ultrafast molecular photoswitching process (occurring within 100 fs) and from the delayed, thermo‐elastic (Arrhenius‐driven) conversion (taking place ≈10 ns). These time‐separated dynamics are also manifested by the observation of damped acoustic oscillations in the time evolution of the lattice volume, whereas no such oscillations are observed in the electronic spin‐state dynamics. Overall, these results suggest the existence of a universal behavior whereby the intramolecular energy barrier between low‐spin and high‐spin states acts as an intrinsic dynamical bottleneck in the out‐of‐equilibrium spin‐state switching dynamics of SCO materials. [ABSTRACT FROM AUTHOR]

Topological semimetals represent a novel class of quantum materials displaying non‐trivial topological states that host Dirac/Weyl fermions. The intersection of Dirac/Weyl points gives rise to essential properties in a wide range of innovative transport phenomena, including extreme magnetoresistance, high mobilities, weak antilocalization, electron hydrodynamics, and various electro‐optical phenomena. In this study, the electronic, transport, phonon scattering, and interrelationships are explored in single crystals of the topological semimetal HfAs2. It reveals a weak antilocalization effect at low temperatures with high carrier density, which is attributed to perfectly compensated topological bulk and surface states. The angle‐resolved photoemission spectroscopy (ARPES) results show anisotropic Fermi surfaces and surface states indicative of the topological semimetal, further confirmed by first‐principle density functional theory (DFT) calculations. Moreover, the lattice dynamics in HfAs2 are investigated both with the Raman scattering and density functional theory. The phonon dispersion, density of states, lattice thermal conductivity, and the phonon lifetimes are computed to support the experimental findings. The softening of phonons, the broadening of Raman modes, and the reduction of phonon lifetimes with temperature suggest the enhancement of phonon anharmonicity in this new topological material, which is crucial for boosting the thermoelectric performance of topological semimetals. [ABSTRACT FROM AUTHOR]

When it comes to sustainable and efficient energy solutions, organic semiconductors can play an important role in thermoelectric applications, since they are non‐toxic, cheap, made of abundant chemical species, and show intrinsically low thermal conductivities. Their electrical conductivity can be optimized via doping. Yet, thermal conduction should be as low as possible and, to this end, the atomic scale mechanisms behind heat transport –e.g. the correlation between morphology and thermal conductivity or the role of doping– should be understood in detail. Fully atomistic molecular dynamics calculations of the lattice thermal conductivity of doped poly(3,4‐ethylenedioxythiophene) (PEDOT) highly ordered, quasi‐crystalline nanofibers are presented here. It is found that the conductivity along the backbone direction is not necessarily the highest, but it depends on the length of the PEDOT chains, thus the degree of anisotropy depends on the the aspect ratio of the nanofiber. Indeed, transport along the lamellar direction can be of the same order or higher than that of the backbone if their lengths are comparable. These results challenge the usual expectation that thermal conduction along the backbone largely exceeds those along the lamellar and π − π direction and have the important consequence that the anisotropy could be leveraged in thermal management applications. [ABSTRACT FROM AUTHOR]

Fabrication of architected materials through self‐assembly of units offers many advantages over monolithic solids including recyclability, reconfigurability, self‐healing, and diversity of emergent properties – all prescribed chiefly by the choice of the building blocks. While self‐assembly is prevalent in biosynthesis, it remains challenging to recapitulate it macroscopically. Recent success in the self‐assembly of 2D ordered open magneto‐elastic lattices from centimeter‐long bar units with sticky magnetic ends, showcasing graceful failure at “magnetic bonds” and re‐assembly under extreme loading. However, it is still unclear how this approach can be generalized to design units that preferably form ordered low‐energy structures with desirable mechanical properties such as ductility, auxetics, and impact resistance. Here, diverse ordered 2D lattice structures are predicted as the self‐assembly outcomes from units with 2 (bar), 3 (Y‐shape), and 4 (cross) branches with magnetic ends. The defect formation is significantly reduced by a computational design approach. Tunable mechanical behavior is shown to be achieved by varying unit shapes and magnet orientations. Cross‐shaped units are identified for their promise in auxetic response and penetration resistance with these findings validated through experiments. The work highlights the potential of self‐assembling magnetic architected materials for adaptive structures, impact mitigation, and energy adsorption. [ABSTRACT FROM AUTHOR]

Lattice dynamics has been widely employed to study various properties of crystalline materials, by revealing the atomic vibration rules with phonon dispersion curves. Modulating lattice‐dynamics‐related factors is an emerging trend in the design of inorganic crystalline solid‐state electrolytes (ICSSEs) with promoted ionic conductivity. Nevertheless, due to complicated interplay of these enormous factors, fundamental understanding of lattice‐dynamics‐influenced ionic transport is still limited. In this review, all related factors are classified into lattice static and dynamic ones based on their variability in ionic transport process, facilitating a methodological evaluation of their individual and interrelated influences. The previous efforts are affirmed to design ICSSEs by constructing potential energy surfaces for ionic transport based on lattice static factors (e.g., ionic arrangement, time‐scale dependent ionic concentration, and lattice softening). As for lattice dynamic factors, the possibility to quantify ionic transport activation energy and to screen the type of migration ions by phonon frequency and amplitude, respectively is validated. Specifically, it is highlighted that the optimization of specific phonon mode and the coupling of both lattice static and dynamic factors are essential to achieve superior ionic transport in ICSSEs. Finally, challenges and opportunities are pointed out in this field, which can potentially guide the future development of ICSSEs. [ABSTRACT FROM AUTHOR]

Strain engineering, as a non‐chemical tuning knob, can enhance the performance of semiconductor devices. Here, an efficient manipulation of light emission is revealed in thin‐layered 2D perovskite strongly correlated to layer numbers of [PbI6]4− octahedron (n) and [C6H5(CH2)2NH3]2(CH3NH3)n‐1PbnI3n+1 (N) by applying uniaxial strains (ɛ) via bending the flexible substrate. As <n> increases from 1 to 3, an efficient light emission redshift (ɛ from −0.97% to 0.97%) is observed from bandgap shrinkage, and the shrinkage rate increases from 1.97 to 10.38 meV/%, which is attributed to the predominant uniaxial intralayer deformation due to the anisotropy of the [PbI6]4− octahedron lattice strain. Conversely, as <N> increases from 7 to 48 for n = 3, the deformation related to bandgap shrinkage rate is more prominent in small‐N flakes (<N> ≈ 7, 15.2 meV/%) but is easily offset in large‐N flakes (<N> ≈ 48, 7.7 meV/%). This anisotropic lattice deformation, meanwhile, inevitably modulates the carrier recombination dynamics of [C6H5(CH2)2NH3]2(CH3NH3)n‐1PbnI3n+1, which is essential for the development of highly efficient photoelectronic devices. [ABSTRACT FROM AUTHOR]

Quantum‐mechanical calculations based on the density functional theory (DFT) enable an effective characterization of a variety of properties of materials at the atomistic level, although at a high computational cost. Here, we fully exploit parallel computing to apply such methods to the study of lattice dynamics and mechanical response of the major oxide constituents of Portland cement clinker: C3S${\rm {C}}_3{\rm {S}}$, C2S${\rm {C}}_{2}{\rm {S}}$, C3A${\rm {C}}_{3}{\rm {A}}$, and C4AF${\rm {C}}_4{\rm {AF}}$. Raman spectra and the evolution of the elastic tensor (and associated mechanical properties) with pressure are predicted for all oxide systems. We devote much attention to the assessment of dynamical and mechanical stability of the many previously proposed polymorphic forms of the most abundant oxide: C3S${\rm {C}}_3{\rm {S}}$. Specifically, five different crystalline models of C3S${\rm {C}}_3{\rm {S}}$ are analyzed: only two turn out to be dynamically stable. The mechanical response of C3S${\rm {C}}_3{\rm {S}}$ is further analyzed as a function of temperature through a quasi‐harmonic description of its lattice dynamics. [ABSTRACT FROM AUTHOR]

Herein, lutecium silicate is used as a rock example to investigate its two high‐pressure phases (7.4 GPa: HP‐II and 25.3 GPa: HP‐III) and lattice dynamics by in situ high‐pressure Raman scattering up to 35.1 GPa. The evidence for a highly symmetrical insulator HP‐III phase is obtained. Importantly, the high‐pressure structure (metastable phases) after pressure quenching is also intercepted, indicating pressure‐induced permanent densification. These findings provide Raman evidence for pressure‐induced successive phase transitions of highly symmetric insulators intercepted in prototype Lu2SiO5 and physical insights to explain the self‐regulation of rare earth‐rich regions in facilitating highly effective global carbon cycling. [ABSTRACT FROM AUTHOR]

Due to their amorphous‐like ultralow lattice thermal conductivity both below and above the superionic phase transition, crystalline Cu‐ and Ag‐based superionic argyrodites have garnered widespread attention as promising thermoelectric materials. However, despite their intriguing properties, quantifying their lattice thermal conductivities and a comprehensive understanding of the microscopic dynamics that drive these extraordinary properties are still lacking. Here, an integrated experimental and theoretical approach is adopted to reveal the presence of Cu‐dominated low‐energy optical phonons in the Cu‐based argyrodite Cu7PS6. These phonons yield strong acoustic‐optical phonon scattering through avoided crossing, enabling ultralow lattice thermal conductivity. The Unified Theory of thermal transport is employed to analyze heat conduction and successfully reproduce the experimental amorphous‐like ultralow lattice thermal conductivities, ranging from 0.43 to 0.58 W m−1 K−1, in the temperature range of 100–400 K. The study reveals that the amorphous‐like ultralow thermal conductivity of Cu7PS6 stems from a significantly dominant wave‐like conduction mechanism. Moreover, the simulations elucidate the wave‐like thermal transport mainly results from the contribution of Cu‐associated low‐energy overlapping optical phonons. This study highlights the crucial role of low‐energy and overlapping optical modes in facilitating amorphous‐like ultralow thermal transport, providing a thorough understanding of the underlying complex dynamics of argyrodites. [ABSTRACT FROM AUTHOR]

Due to their amorphous‐like ultralow lattice thermal conductivity both below and above the superionic phase transition, crystalline Cu‐ and Ag‐based superionic argyrodites have garnered widespread attention as promising thermoelectric materials. However, despite their intriguing properties, quantifying their lattice thermal conductivities and a comprehensive understanding of the microscopic dynamics that drive these extraordinary properties are still lacking. Here, an integrated experimental and theoretical approach is adopted to reveal the presence of Cu‐dominated low‐energy optical phonons in the Cu‐based argyrodite Cu7PS6. These phonons yield strong acoustic‐optical phonon scattering through avoided crossing, enabling ultralow lattice thermal conductivity. The Unified Theory of thermal transport is employed to analyze heat conduction and successfully reproduce the experimental amorphous‐like ultralow lattice thermal conductivities, ranging from 0.43 to 0.58 W m−1 K−1, in the temperature range of 100–400 K. The study reveals that the amorphous‐like ultralow thermal conductivity of Cu7PS6 stems from a significantly dominant wave‐like conduction mechanism. Moreover, the simulations elucidate the wave‐like thermal transport mainly results from the contribution of Cu‐associated low‐energy overlapping optical phonons. This study highlights the crucial role of low‐energy and overlapping optical modes in facilitating amorphous‐like ultralow thermal transport, providing a thorough understanding of the underlying complex dynamics of argyrodites. [ABSTRACT FROM AUTHOR]

One significant class of chemotherapeutic medicines with the ability to overcome drug resistance is metal‐based medications. The creation of novel therapeutic medications with distinct modes of action is required due to the rise in drug resistance, treatment failures, and the scarcity of available treatments. The amino acid isoleucine interacts with the arylidene (synthesized from isatin and 2,6‐diamino‐pyridine) forming the HL Schiff base ligand, which then interacts with some transition metal ions to form the metal complexes. Thermal analysis, spectroscopy (1H‐NMR, IR, mass, and ultraviolet–visible), solid reflectance, magnetic moment, molar conductivity, and elemental analyses were employed for examining the synthesized HL and resultant complexes. Mass spectra besides elemental analyses studies verified the formulae of the Schiff base ligand and metal complexes. All the complexes, except for the Fe(III) complex which is non‐electrolyte, exhibited electrolytic behavior as indicated by their molar conductivity values. The obtained complexes exhibited octahedral geometrical shapes, except for the complexes of Co(II), Ni(II), and Zn(II), which displayed tetrahedral geometry. Thermal analysis showed that the complexes consistently release organic ligands and anionic components following the initial loss of water molecules of hydration. The conducted X‐ray diffraction patterns elucidated their lattice dynamics and not only confirmed the purity of the samples, but also demonstrated that the ligand and complexes of Cr(III), Fe(III), Mn(II), Cu(II), Zn(II), and Cd(II) have a crystalline structure in addition to determination of average size of the crystallites. Scanning electron microscope (SEM) was investigated for Schiff base ligand and Co(II) complex. The complexes demonstrated superior efficacy than HL towards fungal and bacteria organisms against Aspergillus fumigatus and Candida albicans, Salmonella Sp., Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. The MCF‐7 cancer cell was subjected to investigation by synthesized complexes and IC50 values ranged from 12 to 23.1 μg/ml. Molecular docking studies define and anticipate the inhibitory potential and binding mode of the generated ligand with the 1GS4, 2HQ6, 3DJD, and 5JPE receptors. [ABSTRACT FROM AUTHOR]

Ternary nitride semiconductors are rapidly emerging as a promising class of materials for energy conversion applications, offering an appealing combination of strong light absorption in the visible range, desirable charge transport characteristics, and good chemical stability. In this work, it is shown that finite‐temperature lattice dynamics in CuTaN2 – a prototypical ternary nitride displaying particularly strong visible light absorption – exhibit a pronounced anharmonic character that plays an essential role in defining its macroscopic optoelectronic and thermal properties. Low‐frequency vibrational modes that are Raman‐inactive from symmetry considerations of the average crystal structure and unstable in harmonic phonon calculations are found to appear as intensive Raman features near room temperature. The atomic contributions to the anharmonic vibrations are characterized by combining Raman measurements with molecular dynamics and density functional theory calculations. This analysis reveals that anharmonic lattice dynamics have large ramifications on the fundamental properties of this compound, resulting in uniaxial negative thermal expansion and the opening of its bandgap to a near‐optimal value for solar energy harvesting. The atomic‐level understanding of anharmonic lattice dynamics, as well as the finding that they strongly influence key properties of this semiconductor at room temperature, have important implications for design of new functional materials, especially within the emerging class of ternary nitride semiconductors. [ABSTRACT FROM AUTHOR]

Ternary nitride semiconductors are rapidly emerging as a promising class of materials for energy conversion applications, offering an appealing combination of strong light absorption in the visible range, desirable charge transport characteristics, and good chemical stability. In this work, it is shown that finite‐temperature lattice dynamics in CuTaN2 – a prototypical ternary nitride displaying particularly strong visible light absorption – exhibit a pronounced anharmonic character that plays an essential role in defining its macroscopic optoelectronic and thermal properties. Low‐frequency vibrational modes that are Raman‐inactive from symmetry considerations of the average crystal structure and unstable in harmonic phonon calculations are found to appear as intensive Raman features near room temperature. The atomic contributions to the anharmonic vibrations are characterized by combining Raman measurements with molecular dynamics and density functional theory calculations. This analysis reveals that anharmonic lattice dynamics have large ramifications on the fundamental properties of this compound, resulting in uniaxial negative thermal expansion and the opening of its bandgap to a near‐optimal value for solar energy harvesting. The atomic‐level understanding of anharmonic lattice dynamics, as well as the finding that they strongly influence key properties of this semiconductor at room temperature, have important implications for design of new functional materials, especially within the emerging class of ternary nitride semiconductors. [ABSTRACT FROM AUTHOR]

Structural mosaic of rare-earth tri-tellurides (RTe3) inlaid with non-classical structural motifs like the 2D-polytelluride square nets has attracted immense attention owing to their enigmatic chemical bonding, unconventional structure, and harboring charge density wave (CDW) ground states. GdTe3, an archetypal RTe3, is a natural heterostructure of charged and van der Waals (vdW) layers, formed by intercalating vdW gap separated 2D square telluride nets … between the charged double corrugated slabs of n[GdTe]+. Here, we have investigated the evolution of structural distortions along with the electrical and thermal transport properties of GdTe3 across its CDW transition through X-ray pair distribution function analysis, thermal conductivity measurements, Raman spectroscopy and first principles theoretical calculations. The results reveal that the unusual structure of GdTe3 engenders a large anisotropic lattice thermal conductivity by concomitantly hampering the phonon propagation along parallel to the spark plasma sintering (SPS) pressing direction via chemical bonding hierarchy while facilitating phonon propagation along perpendicular to the SPS pressing direction through the metallic Te sheets and phason channel. The low lattice thermal conductivity is attributed to the strong vibrational anharmonicity caused by CDW-induced concerted local lattice distortions of both Gd-Te slab and Te square net, and the robust electron-phonon coupling. [ABSTRACT FROM AUTHOR]

Structural mosaic of rare-earth tri-tellurides (RTe3) inlaid with non-classical structural motifs like the 2D-polytelluride square nets has attracted immense attention owing to their enigmatic chemical bonding, unconventional structure, and harboring charge density wave (CDW) ground states. GdTe3, an archetypal RTe3, is a natural heterostructure of charged and van der Waals (vdW) layers, formed by intercalating vdW gap separated 2D square telluride nets … between the charged double corrugated slabs of n[GdTe]+. Here, we have investigated the evolution of structural distortions along with the electrical and thermal transport properties of GdTe3 across its CDW transition through X-ray pair distribution function analysis, thermal conductivity measurements, Raman spectroscopy and first principles theoretical calculations. The results reveal that the unusual structure of GdTe3 engenders a large anisotropic lattice thermal conductivity by concomitantly hampering the phonon propagation along parallel to the spark plasma sintering (SPS) pressing direction via chemical bonding hierarchy while facilitating phonon propagation along perpendicular to the SPS pressing direction through the metallic Te sheets and phason channel. The low lattice thermal conductivity is attributed to the strong vibrational anharmonicity caused by CDW-induced concerted local lattice distortions of both Gd-Te slab and Te square net, and the robust electron-phonon coupling. [ABSTRACT FROM AUTHOR]

Perovskites have long been materials of interest in solid‐state physics. Their structure leads them to exhibit various characteristics which have both theoretical and practical interest. Lattice dynamics can give a lot of insight into a material's nature such as phase transitions, thus the research presented here focuses on that, by doing a comprehensive vibrational and structural investigation of monocrystalline YAlO3 (YAP). Polarized Raman and infrared (IR) reflectance spectroscopy are used alongside ab initio and classical calculations. In the course of this work, complete Raman spectra have been obtained, confirming new vibrational modes, predicted by ab initio calculations but previously not observed experimentally. IR reflectance spectra have been obtained for the first time for this material. Classical molecular dynamics has been employed to calculate the phonon dispersion and density of states. [ABSTRACT FROM AUTHOR]

Perovskites have long been materials of interest in solid‐state physics. Their structure leads them to exhibit various characteristics which have both theoretical and practical interest. Lattice dynamics can give a lot of insight into a material's nature such as phase transitions, thus the research presented here focuses on that, by doing a comprehensive vibrational and structural investigation of monocrystalline YAlO3 (YAP). Polarized Raman and infrared (IR) reflectance spectroscopy are used alongside ab initio and classical calculations. In the course of this work, complete Raman spectra have been obtained, confirming new vibrational modes, predicted by ab initio calculations but previously not observed experimentally. IR reflectance spectra have been obtained for the first time for this material. Classical molecular dynamics has been employed to calculate the phonon dispersion and density of states. [ABSTRACT FROM AUTHOR]

Self‐trapped exciton (STE) induced broad‐band emission (BE) has sparked considerable interest due to its potential applications in white‐light emitters and optoelectronics. This phenomenon is widely observed in organic–inorganic hybrid perovskites with soft lattice structures, and its physical origin is still under debate. Herein, strong sub‐bandgap STE emission with a large Stokes shift and a photoluminescence quantum yield of up to 9.2% in van der Waals (vdW) layered In4/3P2S6 is reported. Combining comprehensive optical characterizations and theoretical calculations, this concludes that defect‐assisted extrinsic STE is responsible for the BE. The excitonic state can be further localized by hydrostatic pressure, resulting in a threefold PL intensity enhancement. In addition, angle‐resolved polarized Raman demonstrates the anisotropic lattice dynamics in IPS, which may underpin the highly linear anisotropy of the STE emission. This work clarifies the defect, STE, and anisotropy coupling effect in vdW crystal, and provides innovative avenues to modulate the STE luminescence. [ABSTRACT FROM AUTHOR]

Self‐trapped exciton (STE) induced broad‐band emission (BE) has sparked considerable interest due to its potential applications in white‐light emitters and optoelectronics. This phenomenon is widely observed in organic–inorganic hybrid perovskites with soft lattice structures, and its physical origin is still under debate. Herein, strong sub‐bandgap STE emission with a large Stokes shift and a photoluminescence quantum yield of up to 9.2% in van der Waals (vdW) layered In4/3P2S6 is reported. Combining comprehensive optical characterizations and theoretical calculations, this concludes that defect‐assisted extrinsic STE is responsible for the BE. The excitonic state can be further localized by hydrostatic pressure, resulting in a threefold PL intensity enhancement. In addition, angle‐resolved polarized Raman demonstrates the anisotropic lattice dynamics in IPS, which may underpin the highly linear anisotropy of the STE emission. This work clarifies the defect, STE, and anisotropy coupling effect in vdW crystal, and provides innovative avenues to modulate the STE luminescence. [ABSTRACT FROM AUTHOR]

In this work, we present the results of measurements of the Raman spectrum of the √3x√3R30° reconstruction of graphene grown on 4H-SiC(0001), the socalled buffer layer. The extracted Raman spectrum of the buffer layer shows bands, different from those of graphene, which can be attributed to the interaction of the buffer layer with the SiC substrate. In particular, in the highwavenumber region, at least three bands are observed in the wavenumber regions 1,350–1,420, 1,470–1,490 and 1,520–1,570 cm-1. The assignment of the buffer layer bands is supported here by tight-binding simulations of the onephonon density of states for structures with a sufficiently large number of Si-C bilayers for reaching convergence. The converged phonon density of states is found to be in semi-quantitative agreement with the latter two bands, and therefore, the tight-binding predictions of the lattice dynamics of the structure can be used for their assignment to buffer layer vibrations. Namely, the Raman band at about 1,550 cm-1 can be assigned to modified in-plane optical phonon branches of graphene, while the Raman band at about 1,490 cm-1 can be assigned to modified folded parts of these branches inside the Brillouin zone of the buffer layer and can be considered as a Raman fingerprint of the buffer layer. [ABSTRACT FROM AUTHOR]

An important paradigm in the understanding of mixing times of Glauber dynamics for spin systems is the correspondence between spatial mixing properties of the models and bounds on the mixing time of the dynamics. This includes, in particular, the classical notions of weak and strong spatial mixing, which have been used to show the best known mixing time bounds in the high‐temperature regime for the Glauber dynamics for the Ising and Potts models. Glauber dynamics for the random‐cluster model does not naturally fit into this spin systems framework because its transition rules are not local. In this article, we present various implications between weak spatial mixing, strong spatial mixing, and the newer notion of spatial mixing within a phase, and mixing time bounds for the random‐cluster dynamics in finite subsets of ℤd$$ {\mathbb{Z}}^d $$ for general d≥2$$ d\ge 2 $$. These imply a host of new results, including optimal O(NlogN)$$ O\left(N\log N\right) $$ mixing for the random cluster dynamics on torii and boxes on N$$ N $$ vertices in ℤd$$ {\mathbb{Z}}^d $$ at all high temperatures and at sufficiently low temperatures, and for large values of q$$ q $$ quasi‐polynomial (or quasi‐linear when d=2$$ d=2 $$) mixing time bounds from random phase initializations on torii at the critical point (where by contrast the mixing time from worst‐case initializations is exponentially large). In the same parameter regimes, these results translate to fast sampling algorithms for the Potts model on ℤd$$ {\mathbb{Z}}^d $$ for general d$$ d $$. [ABSTRACT FROM AUTHOR]

Bismuth halide perovskites are highly promising for various applications owing to their lower toxicity and greater environmental stability. The temperature‐dependent color tunability of these materials renders them a strong contender for use in smart window applications and temperature sensors. To delve deeper into their properties, the thermochromism and fundamental lattice dynamics are investigated in bismuth halide perovskites through the transmutation of cation and anions, specifically focusing on Cs3Bi2Br9, MA3Bi2Br9, Cs2AgBiBr6, and Cs2AgBiCl6 perovskites. Absorption spectroscopy and powder‐XRD patterns as a function of temperature reveal that 2D‐layered Cs3Bi2Br9 and MA3Bi2Br9 perovskites exhibit significantly greater bandgap changes and thermal expansion compared to 3D connected Cs2AgBiCl6 and Cs2AgBiBr6 perovskites attributed to more space in the 2D connected lattice. The reduction in bandgap and color variation in these perovskites stems from the intricate interplay between electron‐phonon interactions and thermal expansion. Notably, it is found that the type of cation and anion play a crucial role in influencing the degree of thermochromism, as the electron‐phonon coupling depends on this transformation. This study sheds new light on the fundamental mechanisms underlying the thermochromic behavior of bismuth halide perovskites and paves the way for the rational design and engineering of novel thermochromic materials with tailored properties. [ABSTRACT FROM AUTHOR]

The correlation between lattice chemistry and cation migration in high‐entropy Li+ conductors is not fully understood due to challenges in characterizing anion disorder. To address this issue, argyrodite family of Li+ conductors, which enables structural engineering of the anion lattice, is investigated. Specifically, new argyrodites, Li5.3PS4.3Cl1.7−xBrx (0 ≤ x ≤ 1.7), with varying anion entropy are synthesized and X‐ray diffraction, neutron scattering, and multinuclear high‐resolution solid‐state nuclear magnetic resonance (NMR) are used to determine the resulting structures. Ion and lattice dynamics are determined using variable‐temperature multinuclear NMR relaxometry and maximum entropy method analysis of neutron scattering, aided by constrained ab initio molecular dynamics calculations. 15 atomic configurations of anion arrangements are identified, producing a wide range of local lattice dynamics. High entropy in the lattice structure, composition, and dynamics stabilize otherwise metastable Li‐deficient structures and flatten the energy landscape for cation migration. This resulted in the highest room‐temperature ionic conductivity of 26 mS cm−1 and a low activation energy of 0.155 eV realized in Li5.3PS4.3Cl0.7Br, where anion disorder is maximized. This study sheds light on the complex structure–property relationships of high‐entropy superionic conductors, highlighting the significance of heterogeneity in lattice dynamics. [ABSTRACT FROM AUTHOR]

The correlation between lattice chemistry and cation migration in high‐entropy Li+ conductors is not fully understood due to challenges in characterizing anion disorder. To address this issue, argyrodite family of Li+ conductors, which enables structural engineering of the anion lattice, is investigated. Specifically, new argyrodites, Li5.3PS4.3Cl1.7−xBrx (0 ≤ x ≤ 1.7), with varying anion entropy are synthesized and X‐ray diffraction, neutron scattering, and multinuclear high‐resolution solid‐state nuclear magnetic resonance (NMR) are used to determine the resulting structures. Ion and lattice dynamics are determined using variable‐temperature multinuclear NMR relaxometry and maximum entropy method analysis of neutron scattering, aided by constrained ab initio molecular dynamics calculations. 15 atomic configurations of anion arrangements are identified, producing a wide range of local lattice dynamics. High entropy in the lattice structure, composition, and dynamics stabilize otherwise metastable Li‐deficient structures and flatten the energy landscape for cation migration. This resulted in the highest room‐temperature ionic conductivity of 26 mS cm−1 and a low activation energy of 0.155 eV realized in Li5.3PS4.3Cl0.7Br, where anion disorder is maximized. This study sheds light on the complex structure–property relationships of high‐entropy superionic conductors, highlighting the significance of heterogeneity in lattice dynamics. [ABSTRACT FROM AUTHOR]

The excellent luminescence properties and structural dynamics driven by the stereoactivity of the lone pair in a variety of low‐dimensional ns2 metal halides have attracted growing investigations for optoelectronic applications. However, the structural and photophysical aspects of the excited state associated with the lone pair expression are currently open questions. Herein, zero‐dimensional Sn‐based halides with static stereoactive 5 s2 lone pairs are selected as a model system to understand the correlations between the distinctive lone pair expression and the excited‐state structural relaxation and charge carrier dynamics by continuous lattice manipulation. Lattice compression drives 5 s2 lone pair active switching and self‐trapped exciton (STE) redistribution by suppressing excited‐state structural deformation of the isolated SnBr42− units. Our results demonstrate that the static expression of the 5 s2 lone pair results in a red broadband triplet STE emission with a large Stokes shift, while its dynamic expression creates a sky‐blue narrowband emission dominated by the radiative recombination of singlet STEs. Our findings and the photophysical mechanism proposed highlight the stereochemical effects of lone pair expression in controlling light emission properties and offer constructive guidelines for tuning the optoelectronic properties in diverse ns2 metal halides. [ABSTRACT FROM AUTHOR]

The rapidly emerging perovskites hold immense potential for revolutionizing optoelectronic and photovoltaic applications. However, understanding the complex structural dynamics and their response at extreme conditions in robust environments is crucial for optimizing the practical performance of perovskite‐based devices. Previous X‐ray diffraction studies have shown great potential for studying the average structures of these materials, but for more complex analysis at the local atomic level, Raman spectroscopy is a powerful tool. In this study, temperature‐ and pressure‐dependent Raman spectroscopy was used to elucidate the intricate lattice dynamics, phase transitions, and amorphization of FAPbBr3 single crystals at extreme conditions such as low temperature or high pressure. Temperature‐dependent Raman spectra unveiled significant variations in wavenumbers, full width at half maximum, and the vanishing of specific modes at higher temperatures. These were ascribed to symmetry changes caused by two crystallographic phase transitions at −127°C from orthorhombic to tetragonal and at −33°C from tetragonal to cubic phase. In addition, some of the Raman modes disappeared upon heating at −90°C, which was associated with a crystallographically unresolved transition. Pressure‐dependent Raman scattering revealed two phase transitions at 0.3 GPa and 2.2 GPa, which corresponded to the contraction of the PbBr6 octahedra and their tilting distortion, respectively. Further compression uncovered amorphization at 3.6 GPa, characterized by the vanishing of crystalline Raman modes together with the emergence of broad new modes due to the disorder within the crystal structure. Upon pressure release, the original Raman modes were recovered, indicating the reversibility of the pressure‐induced phase transitions. The changes in the Raman spectra were the most significant, especially in the low‐wavenumber lattice modes, when the FAPbBr3 underwent orthorhombic phase transition. It indicates that the inorganic sublattice is affected by the structural change into the orthorhombic phase caused either by temperature or pressure variation. [ABSTRACT FROM AUTHOR]

The phase‐field crystal model allows the study of materials on atomic length and diffusive time scales. It accounts for elastic and plastic deformation in crystal lattices, including several processes such as growth, dislocation dynamics, and microstructure evolution. The amplitude expansion of the phase‐field crystal model (APFC) describes the atomic density by a small set of Fourier modes with slowly‐varying amplitudes characterizing lattice deformations. This approach allows for tackling large, three‐dimensional systems. However, it has been used mostly for modeling basic lattice symmetries. In this work, we present a coarse‐grained description of the hexagonal closed‐packed (HCP) lattice that supports lattice deformation and defects. It builds on recent developments of the APFC model and introduces specific modeling aspects for this crystal structure. After illustrating the general modeling framework, we show that the proposed approach allows for simulating relatively large three‐dimensional HCP systems hosting complex defect networks. [ABSTRACT FROM AUTHOR]

In this study, nanocrystals of antiferromagnetic Cr2O3 are shown via Raman spectroscopy to display peculiar lattice dynamics in terms of phonon softening and the occurrence of an exceptionally strong spin‐phonon coupling. This effect, which is observed to persist well above the onset of the antiferromagnetic ordering temperature, is ascribed to locally correlated spin fluctuations due to the modulation of the magnetic exchange interactions as the chromium atoms oscillate about their equilibrium position. It is found that the spin‐phonon coupling strength is governed by the competing antiferromagnetic and ferromagnetic interactions, where changes in the surface spin configuration can also play a crucial role. Overall, this work proves the size dependence of the interplay between the crystalline and magnetic structures in 3D antiferromagnets varying the surface‐to‐volume ratio and helps establish the fundamentals for a spin‐phonon coupling engineering at the nanoscale via a simple route in a very stable and easy to synthesize material. More importantly, it demonstrates the possibility of coupling phononic excitations with the magnetization dynamics at room temperature, offering a highly prospective nanomaterial for the design of novel magnonic devices. [ABSTRACT FROM AUTHOR]

The Raman and infrared (IR) wavenumbers for the Ruddlesden–Popper Srn + 1BnO3n + 1 (B = Zr, Mo, Sn, Hf) bilayered tetragonal compounds with n = 2 of symmetry D174h and phase I4/mmm (Z = 2) have been analyzed with Wilson's GF matrix method. Theoretical assignments for the optical wavenumbers have been reported for the first time for the bilayered tetragonal Sr3Zr2O7, Sr3Mo2O7, Sr3Sn2O7, and Sr3Hf2O7 compounds in phase I4/mmm with the use of 10 short‐range force constants. Using the available data of the isostructural compounds Sr3Ti2O7, Sr3Mn2O7, and Sr3Fe2O7, we have tried to calculate the vibrational modes of the Sr3B2O7 (B = Zr, Mo, Sn, Hf) compounds in phase I4/mmm by the comparative method. Also, we have compared all these Sr3B2O7 (B = Zr, Mo, Sn, Hf) compounds together in terms of wavenumbers and force constants. The appropriate optical vibrational modes have been assigned to the bilayered tetragonal Sr3B2O7 (B = Zr, Mo, Sn, Hf) compounds in phase I4/mmm. The impact of cation‐B (B = Zr, Mo, Sn, Hf) exchange on the lattice dynamics of the tetragonal bilayered Sr3B2O7 (B = Zr, Mo, Sn, Hf) isostructural compounds has been analyzed by comparison of the zone center vibrational modes, force constants, and bond lengths. To understand the structure more clearly, an attempt is also made to analyze the effect of B‐cations on the affected apical bonds. It was observed that the B‐site substitutions have the least influence on the Sr layer and the equatorial bonds of octahedra; meanwhile, the outer apical bonds of the octahedra have shown the maximum impact. For each normal mode of the bilayered tetragonal Sr3B2O7 (B = Zr, Mo, Sn, Hf) Ruddlesden–Popper phase, the potential energy distribution (PED) has been analyzed for the noteworthy effects of short‐range force constants on calculated wavenumbers. [ABSTRACT FROM AUTHOR]

To build a safe, sustainable, and reliable disposal system for radioactive waste from the nuclear industry, researchers need to understand the physical and chemical aspects of technetium (Tc)‐based oxides. Here, structure–property correlation studies of scheelite‐type AgTcO4 are performed using ab initio calculations. The full phonon dispersion studies reveal the dynamical stability of this compound. The partial phonon density of states, including the complete mode assignment of the vibrational frequencies, shows the maximum involvement of silver (Ag) atoms in the low‐frequency range, while high contribution of oxygen atoms and average contribution from Tc atoms are found throughout the frequency region. The electronic band structure shows that the main contribution to the bottom of the conduction band is Tc d states with a minor contribution from oxygen p states, while the top of the valence band is from Ag d states, which are responsible for the electronic transitions. The frequency‐dependent dielectric functions and computed optical properties show near‐isotropy behavior and, together with absorption peak in the low‐energy range, indicate that AgTcO4 may be a good phosphor when doped with a suitable activator. The estimations are grounded by the available experimental data and also deliver direction for distinct and futuristic applications of AgTcO4. [ABSTRACT FROM AUTHOR]

Electrons in crystals interact closely with quantized lattice degree of freedom, determining fundamental electrodynamic behaviors and versatile correlated functionalities. However, the strength of the electron–phonon interaction is so far determined as an intrinsic value of a given material, restricting the development of potential electronic and phononic applications employing the tunable coupling strength. Here, it is demonstrated that the electron–phonon coupling in SrRuO3 can be largely controlled by multiple intuitive tuning knobs available in synthetic crystals. The coupling strength of quasi‐2D SrRuO3 is enhanced by ≈300‐fold compared with that of bulk SrRuO3. This enormous enhancement is attributed to the non‐local nature of the electron–phonon coupling within the well‐defined synthetic atomic network, which becomes dominant in the limit of the 2D electronic state. These results provide valuable opportunities for engineering the electron–phonon coupling, leading to a deeper understanding of the strongly coupled charge and lattice dynamics in quantum materials. [ABSTRACT FROM AUTHOR]

To build a safe, sustainable, and reliable disposal system for radioactive waste from the nuclear industry, researchers need to understand the physical and chemical aspects of technetium (Tc)‐based oxides. Here, structure–property correlation studies of scheelite‐type AgTcO4 are performed using ab initio calculations. The full phonon dispersion studies reveal the dynamical stability of this compound. The partial phonon density of states, including the complete mode assignment of the vibrational frequencies, shows the maximum involvement of silver (Ag) atoms in the low‐frequency range, while high contribution of oxygen atoms and average contribution from Tc atoms are found throughout the frequency region. The electronic band structure shows that the main contribution to the bottom of the conduction band is Tc d states with a minor contribution from oxygen p states, while the top of the valence band is from Ag d states, which are responsible for the electronic transitions. The frequency‐dependent dielectric functions and computed optical properties show near‐isotropy behavior and, together with absorption peak in the low‐energy range, indicate that AgTcO4 may be a good phosphor when doped with a suitable activator. The estimations are grounded by the available experimental data and also deliver direction for distinct and futuristic applications of AgTcO4. [ABSTRACT FROM AUTHOR]

Titanium disulfide is a quasi‐2D transition‐metal dichalcogenide relevant for various potential applications. To exploit its technological capabilities, it is important to determine its fundamental properties including the lattice dynamics. The TiS2 phonon dispersion curves available to date do not reproduce properly the experimental data for several reasons: i) all available experimental data are not taken into consideration, thus poor theory‐experiment agreements have been obtained; ii) the (unknown) frequency of the infrared mode A2u is erroneously assumed; and iii) such incorrect assignment has propagated in the literature, particularly in phonon dispersion calculations. It is presented here a thorough density functional theory analysis to determine the phonon dispersion curves of TiS2, accounting for the frequencies of all experimental phonon data available to date. These include the frequencies of nine zone‐edge Raman active modes of Ag‐intercalated TiS2, in addition to infrared, Raman, and neutron scattering data. An incorrect frequency assignment of the A2u mode in the literature is thoroughly discussed. Moreover, results of attenuated total reflection terahertz spectroscopy applied to TiS2 are provided. A self‐intercalation paradigm is presented to give a rationale for the temperature dependence of the poorly understood Raman features observed in pristine TiS2 at frequencies above the A1g mode. [ABSTRACT FROM AUTHOR]

Titanium disulfide is a quasi‐2D transition‐metal dichalcogenide relevant for various potential applications. To exploit its technological capabilities, it is important to determine its fundamental properties including the lattice dynamics. The TiS2 phonon dispersion curves available to date do not reproduce properly the experimental data for several reasons: i) all available experimental data are not taken into consideration, thus poor theory‐experiment agreements have been obtained; ii) the (unknown) frequency of the infrared mode A2u is erroneously assumed; and iii) such incorrect assignment has propagated in the literature, particularly in phonon dispersion calculations. It is presented here a thorough density functional theory analysis to determine the phonon dispersion curves of TiS2, accounting for the frequencies of all experimental phonon data available to date. These include the frequencies of nine zone‐edge Raman active modes of Ag‐intercalated TiS2, in addition to infrared, Raman, and neutron scattering data. An incorrect frequency assignment of the A2u mode in the literature is thoroughly discussed. Moreover, results of attenuated total reflection terahertz spectroscopy applied to TiS2 are provided. A self‐intercalation paradigm is presented to give a rationale for the temperature dependence of the poorly understood Raman features observed in pristine TiS2 at frequencies above the A1g mode. [ABSTRACT FROM AUTHOR]

Using a density functional theory‐based thermal transport model, which includes the effects of temperature (T)‐dependent potential energy surface, lattice thermal expansion, force constant renormalization, and higher‐order quartic phonon scattering processes, it is found that the recently synthesized nitride perovskite LaWN3 displays strong anharmonic lattice dynamics manifested into a low lattice thermal conductivity (κL) and a non‐standard κL∝T−0.491 dependence. At high T, the departure from the standard κL∝T−1 law originates in the dual particle‐wave behavior of the heat carrying phonons, which includes vibrations tied to the N atoms. While the room temperature κL=2.98 W mK‐1 arises mainly from the conventional particle‐like propagation of phonons, there is also a significant atypical wave‐like phonon tunneling effect, leading to a 20% glass‐like heat transport contribution. The phonon broadening effect lowers the particle‐like contribution but increases the glass‐like one. Upon T increase, the glass‐like contribution increases and dominates above T = 850 K. Overall, the low κL with a weak T‐dependence points to a new utility for LaWN3 in energy technology applications, and motivates synthesis and exploration of nitride perovskites. [ABSTRACT FROM AUTHOR]

Here, we present our current attempt to intrinsically dope Ni0, Co0, and Fe0 nanoparticles within NiII‐, CoII‐, and FeII‐borate glassy matrices, respectively. The system was prepared by one‐pot reaction of the desired MTII salt with excess NaBH4 through an in‐situ reduction and hydrolysis processes to afford metallic MT0 nanoparticles dispersed into the MT‐BO3 matrix. The composition and structural characteristics of these MT0:MT‐BO3 materials were identified by thermal oxidation, ATR‐IR, X‐ray powder diffraction, and magnetic techniques as glassy/amorphous borate matrices containing magnetic nanoparticles. The electrical conductivity (σ) of cold‐pressed discs of these metal‐doped composites shows that they behave as nonohmic semiconductors within the temperature range of 303 ≤ T ≤ 373 K suggesting a mixed electronic‐ionic conduction. However, their thermal conductivity (κ) occurs through phonon lattice vibration dynamics rather than electronic. The σ/κ ratio shows a steep non‐linear increase from 9.4 to 270 KV−2 in Ni0:Ni‐BO3. In contrast, a moderate‐weak increase is observed for Co0:Co‐BO3 and Fe0:Fe‐BO3 analogs. The obtained materials are examined for thermoelectric (TE) applications by determining their Seebeck coefficient (S) power factor (PF), figure of merit (ZT), and conversion efficiency (η%). All the TE data shows that Ni0:Ni‐BO3 (S, 80 μVK−1; PF, 97.7 mWm−1 K−1; ZT 0.54; η, 2.15%) is a better TE semiconductor than the other two MT0:MT‐BO3. This finding shows that Ni0:Ni‐BO3 is a promising candidate to exploit low‐temperature waste heat from body heat, sunshine, and small domestic devices for small‐scale TE applications. [ABSTRACT FROM AUTHOR]

With first‐principles calculations, a global screening was conducted for the Al‐ and Si‐containing MAB phases by considering their stability, damage tolerance, and magnetic properties, of much interest, where these predicted results are in good agreement with the available experimental ones. By examining the thermodynamics competing with all the experimentally identified phases and lattice dynamics, 29 stable MAB phases are predicted in total. Moreover, the Si‐containing MAB phases are much fewer than the Al‐containing ones, except for the 512 phases. Using the "bond stiffness" model, the strongest covalent bonding is formed between B and M/B atoms while the weakest bonding is formed between M/B and A atoms. For most Al‐containing MAB phases except 512‐type, the ratio of bond stiffness of weakest M‐Al or Al‐Al bonds to the strongest M‐B bonds (kmin/kmax) falls into the range of 1/3–1/2, indicating their high damage tolerance. But this is not true for the Si‐containing ones, with the kmin/kmax greater than 1/2 and strong M‐Si bonds. Furthermore, all the Fe/Mn/Co‐containing MAB phases are screened to be magnetic, with the accurately estimated Curie temperature (TC) and magnetic moment, where Fe2AlB2 and Mn2AlB2 have TC around room temperature, contributing to the future design of magnetic MAB phases for potential applications, such as the magnetic refrigeration and two‐dimensional MBenes. [ABSTRACT FROM AUTHOR]

The growing demands to mitigate climate change and environmental degradation stimulate the rapid developments of rechargeable lithium (Li) battery technologies. Fast Li transports in battery materials are of essential significance to ensure superior Li dynamical stability and rate performance of batteries. Herein, the Li transport mechanisms in solid‐state battery materials (SSBMs) are comprehensively summarized. The collective diffusion mechanisms in solid electrolytes are elaborated, which are further understood from multiple perspectives including lattice dynamics, crystalline structure, and electronic structure. With the exponentially improving performance of computers, atomistic simulations have been playing an increasingly important role in revealing and understanding the Li transport in SSBMs, bridging the gap between experimental phenomena and theoretical models. Theoretical and experimental characterization methods for Li transports are discussed. The design strategies toward fast Li transports are classified. Finally, a perspective on the achievements and challenges of probing Li transports is provided. This article is categorized under:Structure and Mechanism > Computational Materials Science [ABSTRACT FROM AUTHOR]

The issue of polymorphism in molecular crystals is discussed, taking into account the substrate‐mediated structures, that is, structures grown at the interface of different substrates. Bulk and thin films of a compound both share the potentiality to display different crystal forms. However, unlike bulk polymorphs, whose structures are determined by their different molecular packing, thin film structures depend very much on the molecular organization of the organic layers on the substrate, which may, or may not, lead to an ordered structure, depending on the nature of the interface and on the growth conditions. Based on large part in some of the authors' recent works, these thin film structures are classified as distorted bulk, substrate‐selected and substrate‐stabilized polymorphs, with some subtle differences which may yield a polymorph to belong not exclusively to a single one of these categories. Some experiments are then focused upon, involving charge transport at the interface, as well as how far the effect of the surface goes. Furthermore, the authors comment on how the surface‐mediated structures evolve to the single crystal phase in the cases of pentacene and α‐sexithiophene. Finally, the transition from a 3‐ to a 2D regime of growth is shortly discussed in terms of low‐dimensional disorder. [ABSTRACT FROM AUTHOR]

Scientists enquire about materials engineered with high nanoparticle densities with reduced thermal conductivity and excellent thermoelectric performance. An emerging mineral, copper sulfide (CuS) promises a novel paradigm in the proximity of pressure‐driven structural phase transitions to tune its functional and mechanical properties. Though CuS is a thermoelectric material with low lattice thermal conductivity (κl), improvement of its κl remains a challenge to be addressed. Moreover, the underlying mechanism governing pressure‐induced phase transformation and reasons for intrinsically small κl remains completely unexplored. In this study, by combining in‐situ vibrational spectroscopy and ab initio calculations, we reveal that strong phonon anharmonicity under high pressure and low temperature demonstrates a promising approach to decreasing κl efficiently and boosts thermoelectric figure of merit by 2.7 times from its ambient value. A large mode Grüneisen parameter and short lifetimes for acoustic phonons contribute significantly to its thermal transport. [ABSTRACT FROM AUTHOR]

The structural, electronic, lattice dynamic, thermodynamic, and mechanical properties of disodium dimolybdate (Na2Mo2O7) are studied using first‐principles. First, for the crystal structure, the calculated structural parameters have a standard deviation of less than 1.7% compared with the experimental results. Then, the calculated electronic energy band and density of states reveal that Na2Mo2O7 is an insulator and its bandgap is about 2.87 eV. In addition, the linear response method is used to study the lattice dynamics, and the complete phonon dispersion curve, infrared spectra, Raman shift, Born effective charge, and longitudinal optical–transverse optical (LO–TO) splitting characteristic for Na2Mo2O7 are presented for the first time; its thermodynamic properties are worked out based on the phonon density of states (PDOS). Furthermore, the result of elastic anisotropy shows the title compound is a highly anisotropic material. The calculation results in this article are conducive to the development of Na2Mo2O7 and provide guidelines for further experimental research to a certain extent. [ABSTRACT FROM AUTHOR]

The dynamics of the 1D array of single‐walled carbon nanotubes (CNTs), which interact by van der Waals forces, is considered. The molecular dynamics simulation shows that both the mutual displacements of the nanotubes and the deformations of their walls occur in the low‐frequency oscillations domain. The composite model taking into account both types of the nanotubes' motions is developed in the framework of the thin elastic shell theory. Such an approach allows us to reduce the problem to the dynamics of the linear lattice with contact interaction. The dispersion relations are represented analytically and the multichannel propagation that results in phonon interference (the acoustical analog of the Fano resonance) is observed in the presence of the array's irregularities. The latter can be formed with redundant nanotubes, which are placed over the array in the grooves between neighbor sites. The calculations of the transmittance have been performed by the transfer matrix method for several typical configurations. [ABSTRACT FROM AUTHOR]

In order to find a kind of MAX phase material suited for thermal barrier coating (TBC) field, the structural properties, mechanical properties, electronic structure, and thermal properties of Nb2AN (A = Si, Ge, and Sn) MAX phase compounds were studied by density functional theory. The results of cohesive energy, formation enthalpy, elastic constants, and lattice dynamics show that the Nb2AN (A = Si, Ge, and Sn) possess good structural stability, mechanical stability, and dynamical stability. Especially in Nb2SnN phase, although its calculated melting point is not the largest one among them, it possesses the best thermal shock resistance. Its coefficient of thermal expansion fits most suitably to the Ni‐based alloy in 300–1452 K and lowest lattice thermal conductivity force it to be an application prospect TBC material. Its mechanical performance is also good for its own smallest deformation of octahedron structure, highest ductileness, and lowest anisotropy. Electronic structure analysis shows that its lowest Debye temperature ΘD${\Theta _{\bf{D}}}$ comes from its highest ionic degree and lowest covalency. Thus, our research provides a deep theoretical basis for the development of new MAX phase materials. [ABSTRACT FROM AUTHOR]

Lattice dynamical calculations based on atomic potentials are used in the study of energetic materials for vibrational spectra. Features in the potential energy surface, however, can lead to negative eigenvalues of the dynamical matrix which can signify artifactual underlying dynamic or configurational instabilities or underconvergence. In this paper, using crystalline cellulose Iβ as a representative material, we show that a reactive force field (ReaxFF) necessarily yields structures associated with negative eigenvalues. We then propose a modification through a tapering function to eliminate barriers to potential energy minimization and thereby yield structures with no associated negative eigenvalues. Three particular ReaxFF parameterizations are evaluated with the tapering modification by comparing available electronic structure and experimental results from the literature. The newly minimized structures were evaluated using lattice properties, elastic constants, phonon dispersion, temperature‐dependent entropy, and heat capacity. Though the modification allows the models to produce only non‐imaginary vibrational spectra, the variations in computed properties can be large between the parameterizations, especially for those being used outside of the context for which the parameters were developed. Our calculations provide important information for the study of the phonon properties of molecular crystals such as cellulose and energetic materials. [ABSTRACT FROM AUTHOR]

The quest for advanced superionic materials requires understanding their complex atomic dynamics, but detailed studies of the interplay between lattice vibrations and ionic diffusion remain scarce. Here inelastic and quasielastic neutron scattering measurements in the superionic argyrodite Cu7PSe6 are reported, combined with molecular dynamics (MD) based on ab initio and machine‐learned potentials, providing critical insights into the atomistic mechanisms underlying fast ion conduction. The results reveal how long‐range Cu diffusion is limited by intercluster hopping, controlled by selective anharmonic phonons of the crystalline framework. Further, the Green–Kubo simulations reproduce the ultralow lattice thermal conductivity and identify contributions from mobile ions, phonons, and their cross‐correlations. The mode resolved analysis shows that the thermal conductivity is dominated by low‐energy acoustic phonon modes of the overall crystal framework. The analysis of mode‐resolved spectral functions further show that vibrational modes with significant Cu contributions are strongly damped, corresponding to the breakdown of associated phonon quasiparticles. These results highlight the importance of strongly anharmonic effects in superionic systems, in which the traditional quasiharmonic phonon picture is insufficient, and pave the way toward combining machine‐learning accelerated simulations with neutron scattering experiments to rationalize the complex atomic dynamics underlying ionic and thermal transport. [ABSTRACT FROM AUTHOR]

The quest for advanced superionic materials requires understanding their complex atomic dynamics, but detailed studies of the interplay between lattice vibrations and ionic diffusion remain scarce. Here inelastic and quasielastic neutron scattering measurements in the superionic argyrodite Cu7PSe6 are reported, combined with molecular dynamics (MD) based on ab initio and machine‐learned potentials, providing critical insights into the atomistic mechanisms underlying fast ion conduction. The results reveal how long‐range Cu diffusion is limited by intercluster hopping, controlled by selective anharmonic phonons of the crystalline framework. Further, the Green–Kubo simulations reproduce the ultralow lattice thermal conductivity and identify contributions from mobile ions, phonons, and their cross‐correlations. The mode resolved analysis shows that the thermal conductivity is dominated by low‐energy acoustic phonon modes of the overall crystal framework. The analysis of mode‐resolved spectral functions further show that vibrational modes with significant Cu contributions are strongly damped, corresponding to the breakdown of associated phonon quasiparticles. These results highlight the importance of strongly anharmonic effects in superionic systems, in which the traditional quasiharmonic phonon picture is insufficient, and pave the way toward combining machine‐learning accelerated simulations with neutron scattering experiments to rationalize the complex atomic dynamics underlying ionic and thermal transport. [ABSTRACT FROM AUTHOR]