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Chemical reactivity between As and N2 , leading to the synthesis of crystalline arsenic nitride, is here reported under high pressure and high temperature conditions generated by laser heating in a Diamond Anvil Cell. Single crystal synchrotron X-ray diffraction at different pressures between 30 and 40 GPa provides evidence for the synthesis of a covalent compound of AsN stoichiometry, crystallizing in a cubic P213 space group, in which each of the two elements is single-bonded to three atoms of the other and hosts an electron lone pair, in a tetrahedral 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.

Carbon disulfide, CS2, mp = 161.7 K, has been crystallized in situ in a diamond-anvil cell at 295 K and 1.26 GPa to give an orthorhombic Cmca structure. No phase transitions occur with further increasing pressure till the polymerization onset at 8 GPa. The crystal structure was determined by direct methods from single-crystal X-ray diffraction at 295 K at two pressure points: 1.8 and 3.7 GPa (esd’s in the lengths of CS bond 0.0001 nm). The molecular rearrangements have been rationalized by the close packing and equidistant S···S intermolecular interactions enforced by pressure. Although only slight lengthening of the covalent double CS bond has been observed till 3.7 GPa, the intensified intermolecular S···S and C···S interactions reveal the possible reaction pathways of pressure-induced polymerization of CS2.