Black phosphorus was compressed at room temperature across the A17, A7 and simple‐cubic phases up to 30 GPa, using a diamond anvil cell and He as pressure transmitting medium. Synchrotron X‐ray diffraction showed the persistence of two previously unreported peaks related to the A7 structure in the pressure range of the simple‐cubic phase. The Rietveld refinement of the data demonstrates the occurrence of a two‐step mechanism for the A7 to simple‐cubic phase transition, indicating the existence of an intermediate pseudo simple‐cubic structure. From a chemical point of view this study represents a deep insight on the mechanism of interlayer bond formation during the transformation from the layered A7 to the non‐layered simple‐cubic phase of phosphorus, opening new perspectives for the design, synthesis and stabilization of phosphorene‐based systems. As superconductivity is concerned, a new experimental evidence to explain the anomalous pressure behavior of Tc in phosphorus below 30 GPa is provided.

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Phosphorene, the 2D material derived from black phosphorus, has recently attracted a lot of interest for its properties, suitable for applications in materials science. The physical features and the prominent chemical reactivity on its surface render this nanolayered substrate particularly promising for electrical and optoelectronic applications. In addition, being a new potential ligand for metals, it opens the way for a new role of the inorganic chemistry in the 2D world, with special reference to the field of catalysis. The aim of this review is to summarize the state of the art in this subject and to present our most recent results in the preparation, functionalization, and use of phosphorene and its decorated derivatives. We discuss several key points, which are currently under investigation: the synthesis, the characterization by theoretical calculations, the high pressure behavior of black phosphorus, as well as its decoration with nanoparticles and encapsulation in polymers. Finally, device fabrication and electrical transport measurements are overviewed on the basis of recent literature and the new results collected in our laboratories.

High pressure state-of-the-art synchrotron XRD in black-phosphorus has solved apparent contradictions about the stability of the A7 layered structure in pnictogens, highlighting the importance of the s–p orbital mixing in the formation of the p-sc structure.

Chemical reactivity between As and N 2 ,l eading to the synthesis of crystalline arsenic nitride,i sh ere reported under high pressure and high temperature conditions generated by laser heating in ad iamond anvil cell. Single-crystal synchrotron X-rayd iffraction at different pressures between 30 and 40 GPaprovides evidence for the synthesis of acovalent compound of AsN stoichiometry,crystallizing in acubic P2 1 3 space group,inwhich eachofthe two elements is single-bonded to three atoms of the other and hosts an electron lone pair,i n at etrahedral anisotropic coordination. The identification of characteristic structural motifs highlights the key role played by the directional repulsive interactions between non-bonding electron lone pairs in the formation of the AsN structure. Additional data indicate the existence of AsN at room temperature from 9.8 up to 50 GPa. Implications concern fundamental aspects of pnictogens chemistry and the synthesis of innovative advanced materials.

Recently, simple carbon based polymers have been synthesized at high pressures in silicalite, a pure SiO2 zeolite with a 3D system of mutually interconnected microchannels. These protocols permitted otherwise unstable polymers to be stabilized and protected from the atmosphere and to obtain an entirely novel class of nanocomposites with modified physical properties. In these 3-D systems, channel interconnection may prevent ideal, isolated polymer chains to be obtained. In this work, the high pressure (5–10 GPa) synthesis of two archetypal, linear polymers polyacetylene (PA) and polycarbonyl (pCO) in the 1D channel system of the pure SiO2 zeolite ZSM-22 (TON) has been performed. The two resulting nanocomposites PA/TON and pCO/TON are organic/inorganic composite materials, which are good candidates as highly directional semiconductors and high energy density materials, respectively. The synthesis was performed in diamond anvil cells, starting from dense C2H2 and CO, confined in ZSM-22, and the nanocomposites were recovered at ambient conditions. The monomer polymerization was proven by IR spectroscopy and synchrotron X-ray diffraction measurements. DFT calculations were performed in order to obtain insight about the configurations of the 1D embedded polymers.

No abstract

Carbon dioxide is a widespread simple molecule in the Universe. In spite of its simplicity it has a very complex phase diagram, forming both amorphous and crystalline extended phases above 40 GPa. The stability range and nature of these phases are still debated, especially in view of their possible role within the deep carbon cycle. Here, we report static synchrotron X-ray diffraction and Raman high-pressure experiments in the megabar range providing evidence for the stability of the polymeric phase V at pressure-temperature conditions relevant to the Earth’s lowermost mantle. The equation of state has been extended to 120 GPa and, contrary to earlier experimental findings, neither dissociation into diamond and ε-oxygen nor ionization was observed. Severe deviatoric stress and lattice deformation along with preferred orientation are removed on progressive annealing, thus suggesting CO2-V as the stable structure also above one megabar.