On the Crystal Chemistry of Inorganic Nitrides: Crystal-Chemical Parameters and Opportunities in the Exploration of Their Compositional Space

Abstract

The scarcity of nitrogen in Earth's crust, combined with challenging synthesis, have made inorganic nitrides a relatively-unexplored class of compounds compared to their naturally-abundant oxide counterparts. To facilitate exploration of their compositional space via a priori modeling, and to help a posteriori structure verification not limited to inferring the oxidation state of redox-active cations, we derive a suite of bond-valence parameters and Lewis-acid strength values for 76 cations observed bonding to N 3-, and further outline a baseline statistical knowledge of bond lengths for these compounds. We examine structural and electronic effects responsible for the functional properties and anomalous bonding behavior of inorganic nitrides, and identify promising venues for exploring uncharted compositional spaces beyond the reach of highthroughput computational methods. We find that many mechanisms of bond-length variation ubiquitous to oxide and oxysalt compounds (e.g., lone-pair stereoactivity, the Jahn-Teller and pseudo Jahn-Teller effects) are similarly pervasive in inorganic nitrides, and are occasionally observed to result in greater distortion magnitude than their oxide counterparts. We identify inorganic nitrides with multiply-bonded metal ions as a promising venue in heterogeneous catalysis, e.g. in the development of a post-Haber-Bosch process proceeding at milder reaction conditions, thus representing further opportunity for exploring the functional properties of this emerging class of materials.

Two-step solid-state synthesis of ternary nitride materials

“…Ternary metal nitrides remain under-explored as new functional inorganic materials, 1 even though a large number of new nitride compositions and structure types have been recently predicted. [2][3][4][5] The underutilized potential of nitride materials stems from their difficult synthesis, with few successful reactions that do not require extreme temperature or pressure conditions. This is because molecules with nitrogen triple bonds, including dinitrogen, have some of the strongest chemical bonds, 6 and because inorganic nitrides are often highly refractory materials used in ultra-hard coatings (TiN, Si 3 N 4 ) 7 and high temperature lubricants (BN).…”

Bond-Length Distributions for Ions Bonded to Oxygen: Results for the Transition Metals and Quantification of the Factors Underlying Bond-Length Variation in Inorganic Solids

“…While this series has focused on bonds to oxygen, it is desirable that similar studies be done in the future for other anions; Gagné recently published a similar study for cations bonded to N 3-in inorganic compounds. 28 This article is the fifth and last of a series in which we describe bond-length data for ions bonded to oxygen in inorganic crystals. In this series, we have examined the distribution of bond lengths for 135 ions bonded to oxygen in 460 configurations (on the basis of coordination number), using 177,446 bond lengths extracted from 9210 crystal structures refined since 1975; these data cover most ions of the periodic table and the coordination environment in which they occur in inorganic compounds.…”