Structure prediction of binary pernitride MN2 compounds (M=Ca, Sr, Ba, La, and Ti)

Semiconductors with Chiral Crystal Structure in Group IVB Transition Metal Pernitrides

Group IVB transition metal (TM) nitrides rarely exhibit semiconductor phase, except for TM3N4 (TM = Ti, Zr, and Hf) compounds. In this study, using the ab-initio calculations based on density...

Synthesis and high-pressure studies of strontium diazenide by synchrotron X-ray diffraction and DFT calculations

In this work, strontium diazenide (SrN2) was synthesized using strontium azide as a starting material in a Walker-type module under high-pressure and high-temperature conditions. The synthesized SrN2 was further studied under high pressure up to 43.2 GPa using in situ synchrotron X-ray diffraction to supplement the high-pressure exploration of alkaline earth diazenides. The SrN2 underwent a possible phase transition from a tetragonal structure into an orthorhombic structure at 12.0 GPa. SrN2 shows anisotropic compressibility due to the orientation of the diazenide anions. The bulk modulus of SrN2 is 132.4 (10.2) GPa, which is larger than that of Sr(N3)2. The larger bulk modulus of SrN2 is attributed to the stronger covalent strength between Sr and N atoms in SrN2, which is confirmed by our theoretical calculations.

Synthesis, structure, and properties of SrC(NH)3 , a nitrogen-based carbonate analogue with the trinacria motif

Strontium guanidinate, SrC(NH)3 , the first compound with a doubly deprotonated guanidine unit, was synthesized from strontium and guanidine in liquid ammonia and characterized by X-ray and neutron diffraction, IR spectroscopy, and density-functional theory including harmonic phonon calculations. The compound crystallizes in the hexagonal space group P63 /m, constitutes the nitrogen analogue of strontium carbonate, SrCO3 , and its structure follows a layered motif between Sr(2+) ions and complex anions of the type C(NH)3 (2-) ; the anions adopt the peculiar trinacria shape. A comparison of theoretical phonons with experimental IR bands as well as quantum-chemical bonding analyses yield a first insight into bonding and packing of the formerly unknown anion in the crystal.

Phase stability, chemical bonding and mechanical properties of titanium nitrides: a first-principles study

New crystal structures of Ti–N compounds: (a) Immm-Ti₃N₂ at 0 GPa, (b) C2/m-Ti₄N₃ at 0 GPa, (c) C2/m-Ti₆N₅ at 0 GPa, and (d) Cmcm-Ti₂N at 60 GPa.