Nitride
materials are of considerable interest due to their fundamental
importance and practical applications. However, synthesis of transition
metal nitrides often requires extreme conditions, e.g., high temperature
and/or high pressure, slowing down the experimental discovery. Using
global structure search methods in combination with first-principles
calculations, we systematically explore the stoichiometric phase space
of iron–nitrogen compounds on the nitrogen-rich side at ambient
and high pressures up to 100 GPa. Diverse stoichiometries in the Fe–N
system are found to emerge in the phase diagram at high pressures.
Significantly, FeN4 is found to be stable already at ambient
pressure. It undergoes a polymerization near 20 GPa which results
in a high energy density. Accompanying the polymerization, FeN4 transforms from a direct band gap semiconductor to ferromagnetic
metal. We also predict several phase transitions in FeN and FeN2 at high pressure, and the results explain the previous experimental
observations by comparing the X-ray diffraction patterns. Stepwise
formation of polynitrogen species is observed following the increment
of nitrogen content in the stoichiometry, from isolated N atoms in
FeN, to the N2 unit in FeN2 and Fe3N8, to the N6 unit in Fe3N8 and FeN3, and to the N∞ chain in FeN4, FeN6, and FeN8. Ultra-incompressibility
is found in marcasite-FeN2, FeN3, and FeN4 along particular crystalline directions, while high energy
density, 1.37–2.02 kJ g–1, is expected for
FeN4, FeN6, and FeN8. Our results
shed light on understanding the chemistry of transition metal polynitrides
under pressure and encourage experimental synthesis of newly predicted
iron nitrides in the near future.
Accurate doping at special atomic sites can achieve effective control of active centers for oxygen evolution reactions (OER), leading to the synthesis of active intermediates with higher conversion efficiency. Here...
Understanding the fundamental principle of catalytic performance and the mechanism of multimetal-based electrocatalysts is essential for the rational design of advanced renewable energy systems. Here, the highly crystalline MMMoB4 (M=Fe,...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.