Synthesis and characterization of nitrides of iridium and palladium

Abstract

We describe the synthesis of nitrides of iridium and palladium using the laser-heated diamond anvil cell. We have used the in situ techniques of x-ray powder diffraction and Raman scattering to characterize these compounds and have compared our experimental findings where possible to the results of first-principles theoretical calculations. We suggest that palladium nitride is isostructural with pyrite, while iridium nitride has a monoclinic symmetry and is isostructural with baddeleyite.

Phase stabilities at a glance: Stability diagrams of nickel dipnictides

“…[38][39][40][41][42][43][44][45][46][47] Actually, the discovery of novel dinitride compounds was successful recently (OsN 2 , IrN 2 , PtN 2 ) [38][39][40]48 -driven by promising properties like hardness or superconductivity. This situation is seen as a starting point for the question on the prediction of the relative stability of known and unknown compounds and structures with respect to possible polymorphs and the decomposition into more stable products.…”

Predicting new superhard phases

“…Very recently, a new family of materials formed by heavy transition metals and light elements are proposed to be potential superhard since heavy transition metals can basically introduce high valence electron density into the compounds to resist both elastic and plastic deformation. Many these compounds have then been successfully synthesized, such as, transition metal nitrides [17][18][19][20][21], carbides [22], and borides [23][24][25][26][27][28]. These compounds possess ultrahigh bulk moduli (428 GPa for IrN 2 [20]) comparable with those of the traditional superhard materials.…”

Thermodynamic Ground States of Platinum Metal Nitrides

“…A rotation of dimers such that two pairs point in the [111] and [111] direction, respectively, results in the marcasite structure, the predicted ground state phase of RuN 2 , RhN 2 and OsN 2 [7]. A small lattice distortion of marcasite then yields the monoclinic baddeleyite (CoSb 2 ) structure found in IrN 2 [5,7].The low-pressure phase diagrams of these systems are still not well understood. In particular their degree of thermodynamic stability has only been addressed briefly [3], where it was proposed that the Pt-N compound is only metastable at low pressures.…”

“…all these compounds have been shown to be at least metastable at ambient conditions. The resulting crystal structures have been investigated by several groups both experimentally and theoretically [2][3][4][5][6][7][8], and by now consensus has been reached concerning the observed crystal structures and stoichiometry (one metal atom for every nitrogen dimer). PtN 2 and PdN 2 are formed in the pyrite crystal structure, a cubic phase with the metal atoms occupying fcc sites.…”