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Experimental studies of hydrogen at high pressure are challenging, so theory is central to understanding its phase behaviour; however, computed phase diagrams do not agree with previous measurements. Here, the authors use a quantum Monte Carlo method and present results in qualitative agreement with experiment.

A global network of researchers was formed to investigate the role of human genetics in SARS-CoV-2 infection and COVID-19 severity; this paper reports 13 genome-wide significant loci and potentially actionable mechanisms in response to infection.

The melting temperature of hydrogen drops at high pressures, which suggests the possible emergence of a low-temperature liquid state of metallic hydrogen. Chen et al.confirm the existence of this phase in simulations and show how the quantum motion of the protons has a critical role in its stabilization.

Superionic states of matter simultaneously exhibit some of the properties of a liquid and of a solid. Detailed numerical simulations predict two superionic phases in mixtures of helium and water.

Simulations using machine-learning-based interatomic potentials in dense hydrogen overcome system size and timescale limitations, providing evidence of a supercritical behaviour of high-pressure liquid hydrogen and reconciling theoretical and experimental discrepancies.

Superionic water is believed to exist in the interior of ice giant planets. By combining machine learning and free-energy methods, the phase behaviours of water at the extreme pressures and temperatures prevalent in such planets are predicted.

Researchers employ machine learning-driven simulations to investigate the behavior of oxygen under extreme pressures up to 1,000 TPa. They identify stable phases and obtain information on the melting line and thermal properties of oxygen, improving our understanding of the structure and evolution of white dwarfs.

Studies of the Earth's atmosphere have shown that more than 90% of xenon is depleted — the so-called missing Xe paradox. Now a theoretical study shows that Xe and Fe/Ni can form inter-metallic compounds of XeFe₃ and XeNi₃ under conditions found in the Earth's inner core, and could provide a solution to the puzzle.

An analysis of 24,202 critical cases of COVID-19 identifies potentially druggable targets in inflammatory signalling (JAK1), monocyte–macrophage activation and endothelial permeability (PDE4A), immunometabolism (SLC2A5 and AK5), and host factors required for viral entry and replication (TMPRSS2 and RAB2A).

Obtainment of hydrogen-rich metal hydrides that are high-temperature superconductors has been demonstrated under very high pressure, but is still largely unexplored. Here the authors synthesize CeH₉, with a structure related to solid metallic hydrogen, at relatively low pressure and without need for heating.

Genome-wide ancient DNA data from individuals from the Middle Bronze Age to Iron Age documents large-scale movement of people from the European continent between 1300 and 800 bc that was probably responsible for spreading early Celtic languages to Britain.

Whole-genome sequencing, transcriptome-wide association and fine-mapping analyses in over 7,000 individuals with critical COVID-19 are used to identify 16 independent variants that are associated with severe illness in COVID-19.

Steve Brown and colleagues report an analysis of 20 phenotyping tests, including 413 data parameters, across 449 mutant mouse alleles. They identify widespread pleiotropy and assign putative functions to genes that lacked previous phenotypic annotation.

A genome-wide association study of critically ill patients with COVID-19 identifies genetic signals that relate to important host antiviral defence mechanisms and mediators of inflammatory organ damage that may be targeted by repurposing drug treatments.

Ditches have many overlooked environmental and societal roles, including impact on biodiversity and pollution, and management strategies to enhance their multifunctional landscape-scale benefits are needed, according to a review of physical, biotic, chemical, and human factors.

The machine that houses the world's largest laser, and which stands in for the starship Enterprise's warp core in the film Star Trek Into Darkness, has compressed diamond to the density of lead. See Letter p.330

Magnesium Oxide and water are abundant in the interior of planets. Here, the authors predict three new MgO-H₂O compounds: Mg₂O₃H₂, MgO₃H₄ and MgO₄H₆, and they exhibit superionic behavior in planetary interior conditions.

Metal-fluoride-based lithium-ion battery cathodes are typically classified as conversion materials because reconstructive phase transitions are presumed to occur upon lithiation. Metal fluoride lithiation is now shown to be dominated instead by diffusion-controlled displacement mechanisms.

What happens to a crystal placed under a huge pressure? In the case of aluminium, it is now shown that the standard, low-pressure close-packed structure transforms into an open one, with incommensurate host–guest arrangement. The findings could have important implications for a wider range of elements.

Little was known about the properties of hydrogen under extreme pressure. Experiments now reveal key details about the arrangement of molecules in several of the element’s high-pressure phases.

Ammonia is an important compound for producing pharmaceuticals, fertilisers and explosives. It is known to form hydrogen-bonded solids at high pressure, but ionic solids of ammonium amide are now predicted at even higher pressure.

Nitrogen-doped lutetium hydride, recently proposed as a superconductor at near-ambient conditions, features distinct color changes from blue to pink to red as a function of pressure. Using theoretical calculations, the authors identify the pink phase as hydrogen-deficient LuH₂ and find that this phase is not a phonon-mediated superconductor near room temperature. Further, the color is controlled by the concentration of hydrogen vacancies.

Superconductivity was recently reported experimentally in nitrogen-doped lutetium hydride with T_c = 294 K at a pressure of 1 GPa. Here, via theoretical calculations, the authors find no structures capable of supporting conventional superconductivity in the Lu-N-H system at ambient pressure.

Solid helium is predicted to become a metal at extraordinarily high pressures of 25 TPa. Here, the authors predict that helium becomes an excitonic insulator just below the metallization pressure, and a superconductor just above the metallization pressure.

The only known compound of sodium and hydrogen is ionic NaH, but theory predicts the existence of polyhydrides at high pressure. Here, the authors report observations of the formation of polyhydrides above 40 GPa and 2000 K, supporting the idea of multicentre bonding in a material with unusual stoichiometry.

Under conditions of Earth’s deep lower mantle, hydrogen ions diffuse freely through the FeOOH lattice framework and electrical conductivity increases rapidly, according to electrical conductivity experiments and first-principles simulations.

A hurdle for designing improved capture materials is the lack of adequate tools to characterise how carbon dioxide adsorbs. Here the authors developed a method to understand how carbon dioxide is captured by materials. Their ¹⁷O solid-state NMR spectroscopy reveals clear signatures for different capture products.

Monolayer water exhibits rich and diverse phase behaviour that is highly sensitive to temperature and the van der Waals pressure acting within the nanochannel.

The reactivity of small molecule gases at high pressure has implications for astrochemistry. Here helium is shown in silico to form stable compounds with water and ammonia at gigapascal pressures.

Ice is one of the most well-studied condensed matter systems, yet new phases are still being discovered. Here the authors report a large-scale computational study of the configuration space of water ice, creating a navigable “sketch-map” including new predicted phases as well as relationships between different structures.

Haniffa and colleagues provide diagnostic aids, potential biomarkers for disease staging and therapeutic strategies for cutaneous T cell lymphoma.

The role of stoichiometric defects in the superconducting polyhydride LaH_10±δ has received little attention so far. Here, the authors use molecular-dynamics simulations to show that a small amount of stoichiometric defects will cause quantum proton diffusion in the otherwise rigid lanthanum lattice.

The reactivity of the noble gases—a notoriously inert group—at high pressures is intriguing. Now, two xenon oxides with unusual stoichiometries, Xe₂O₅ and Xe₃O₂, have been synthesized above 78 GPa and predicted to be stable above 50 GPa, indicating that xenon is more reactive than previously thought.

Several rare earth carbides are superconducting at ambient pressure and low temperature. Here global structure searching predicts high-pressure metallic phases of yttrium dicarbide with phonon-mediated superconductivity and increased carbon network evolution from dimers to sheets with increasing pressure.

Verification efforts of density-functional theory (DFT) calculations are of crucial importance to evaluate the reliability of simulation results. In this Expert Recommendation, we suggest metrics for DFT verification, illustrating them with an all-electron reference dataset of 960 equations of state covering the whole periodic table (hydrogen to curium) and discuss the importance of improving pseudopotential codes.

Ab initio calculations are used to determine the contribution of quantum fluctuations to the crystal structure of the high-pressure superconducting phase of H₃S and D₃S; the quantum nature of the proton is found to fundamentally change the superconducting phase diagram of H₃S.

The Schizophrenia Psychiatric Genome-Wide Association Study Consortium reports five genetic loci newly associated with risk of schizophrenia, involving 17,836 cases of schizophrenia and 33,859 healthy controls. The new locus with the strongest support of association was located within an intron for microRNA 137, a known regulator of neuronal development. Four other genome-wide significant loci for schizophrenia contain predicted targets of MIR137, suggesting that disruption to pathways involving MIR137 may be an etiologic mechanism in schizophrenia.

Recent breakthroughs in crystal structure prediction have enabled the discovery of new materials and of new physical and chemical phenomena. This Review surveys structure prediction methods and presents examples of results in different classes of materials.