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What is the likelihood that a hypothetical material - the combination of a composition and crystal structure - can be formed? Underpinning the reliability of predictions for local or global...

The Fermi surface is an important tool for understanding the electronic, optical, and magnetic properties of metals and doped semiconductors (Dugdale, 2016). It defines the surface in reciprocal space that divides unoccupied and occupied states at zero temperature. The topology of the Fermi surface impacts a variety of quantum phenomena including superconductivity, topological insulation, and ferromagnetism, and it can be used to predict the complex behaviour of systems without requiring more detailed computations. For example: (i) large nested Fermi sheets are a characteristic of charge density ordering (Lomer, 1962); (ii) the size and position of Fermi pockets are indicators of high-performance thermoelectrics (Park et al., 2020); and (iii) the average group velocities across the Fermi surface control the sensitivity of materials for dark matter detection (Inzani et al., 2021). IFermi is a Python library for the generation, analysis, and visualisation of Fermi surfaces that can facilitate sophisticated analyses of Fermi surface properties. * equal contribution † equal contribution Ganose et al., (2021). IFermi: A python library for Fermi surface generation and analysis.

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Thermoelectric materials offer the possibility of enhanced energy efficiency due to waste heat scavenging. Based on their high-temperature stability and ease of synthesis, efficient oxide-based thermoelectrics remain a tantalizing research goal; however, their current performance is significantly lower than the industry standards such as Bi2Te3 and PbTe. Among the oxide thermoelectrics studied thus far, the development of n-type thermoelectric oxides has fallen behind that of p-type oxides, primarily due to limitations on the overall dimensionless figure of merit, or ZT, by large lattice thermal conductivities. In this article, we propose a simple strategy based on chemical intuition to discover enhanced n-type oxide thermoelectrics. Using state-of-the-art calculations, we demonstrate that the PbSb2O6-structured BaBi2O6 represents a novel structural motif for thermoelectric materials, with a predicted ZT of 0.17–0.19. We then suggest two methods to enhance the ZT up to 0.22, on par with the current best earth-abundant n-type thermoelectric at around 600 K, SrTiO3, which has been much more heavily researched. Our analysis of the factors that govern the electronic and phononic scattering in this system provides a blueprint for optimizing ZT beyond the perfect crystal approximation.

Antimony sulfide (Sb 2 S 3 ) and selenide (Sb 2 Se 3 ) are emerging earth-abundant absorbers for photovoltaic applications. Solar cell performance depends strongly on charge-carrier transport properties, but these remain poorly understood in Sb 2 X 3 (X = S, Se). Here we report band-like transport in Sb 2 X 3 , determined by investigating the electron–lattice interaction and theoretical limits of carrier mobility using first-principles density functional theory and Boltzmann transport calculations. We demonstrate that transport in Sb 2 X 3 is governed by large polarons with moderate Fröhlich coupling constants (α ≈ 2), large polaron radii (extending over several unit cells), and high carrier mobility (an isotropic average of >10 cm 2 V –1 s –1 for both electrons and holes). The room-temperature mobility is intrinsically limited by scattering from polar phonon modes and is further reduced in highly defective samples. Our study confirms that the performance of Sb 2 X 3 solar cells is not limited by intrinsic self-trapping.

Symmetry breaking in covalent organic frameworks (COFs) lowers the energy and increases the valence to conduction band separation of the material.

The importance of metal migration during multi-electron redox activity has been characterized, revealing a competing demand to satisfy bonding requirements and local strains in structures upon alkali intercalation.The local structural evolution required to accommodate alkali intercalation in Y2(MoO4)3 and Al2(MoO4)3 during Li (de)insertion has been contrasted by operando characterization methods, including X-ray absorption spectroscopy and diffraction, along with nuclear magnetic resonance measurements. Computational modeling further rationalized behavioral differences. The local structure of Y2(MoO4)3 was maintained upon lithiation while the structure of Al2(MoO4)3 underwent substantial local atomic rearrangements as the stronger ionic character of the bonds in Al2(MoO4)3 allowed Al to mix off its starting octahedral position to accomodate strain during cycling. However, this mixing was prevented in the more covalent Y2(MoO4)3 which could only accommodate this strain through rotational motion of the polyhedral subunits. Knowing that an increased ionic character can facilitate the diffusion of redox-inactive metals when cycling multi-electron electrodes offers a powerful design principle, to improve kinetics for example, when identifying next-generation intercalation hosts that can store more than one electron per transition metal.