Experimental evidence for pressure-induced first order transition in cerium nitride from B1 to B10 structure type

Abstract

The crystal structure of CeN was investigated up to pressures of 82 GPa, using diamond anvil cell powder X-ray diffraction in two experiments with He and Si-oil as the pressure transmitting media. In contrast to previous reports, we do not observe the B2 (CsCl type) structure at high pressure. Instead, the structural phase transition, starting at 65 GPa, from the ambient rock salt B1 structure results in a distorted CsCl-like B10 structure, irrespective of the pressure medium. Our result unambiguously confirms two recent density functional theory (DFT) studies predicting the B10 phase to be stable at these pressures, rather than the B2 (CsCl type) phase previously reported. The B10 structure appears to approach the B2 structure as pressure is increased further, but DFT calculations indicate that an L1 0 structure (AuCu type) is energetically favored.

Experimental equation of state of 11 lanthanide nitrides (NdN to LuN) and pressure induced phase transitions in NdN, SmN, EuN, and GdN

“…In a recent investigation of CeN, we found that this compound undergoes a B1 to B10 transition starting at roughly 65 GPa. 16 This result was in accordance with two theoretical papers that predicted this phase to be stable by calculations of the phonon dispersion within the density functional theory (DFT) framework. 17,18 As a result, a B1 to B10 transition has now been experimentally observed for the first three members of the LnN series, LaN, 19 CeN, 16 and PrN, 20 while theoretical studies on LuN 21,22 indicate a B1 to B10 phase transition at ∼240 GPa.…”

“…16 This result was in accordance with two theoretical papers that predicted this phase to be stable by calculations of the phonon dispersion within the density functional theory (DFT) framework. 17,18 As a result, a B1 to B10 transition has now been experimentally observed for the first three members of the LnN series, LaN, 19 CeN, 16 and PrN, 20 while theoretical studies on LuN 21,22 indicate a B1 to B10 phase transition at ∼240 GPa. This suggests that the pressure-induced structural transition could be a common feature throughout the LnN series.…”

“…28,29 As the macroscopic strain is included in the analysis, the use of different PTMs, even the use of a bad PTM (i.e., one that introduces non-hydrostatic strain already at low pressures) such as Si-oil, has no influence on the refined unit cell parameters. 16 Further details about the workflow for data integration and analysis can be found in our previous study of CeN. 16 The equations of state were fitted using the EoSFit 7c program, 30 which was also used to calculate the K 0 -K 0 0 correlation plots.…”

High-Pressure Computational Search of Trivalent Lanthanide Dinitrides

“…Mononitrides with a trivalent rare-earth cation are reported to form simple packed structures under pressure (B1, B2, B10) − with a suggested formal oxidation state configuration M 3+ N 3– , resulting in small-to-wide band gap semiconductors . On the contrary, several valence configurations have been proposed to explain the nature of the nitrogen chemical bonding and its relation to the physical properties of MN 2 materials.…”

High pressure computational search of trivalent lanthanide di-nitrides

“…17 Moreover, it is known that the alloying of nitrogen with alkali or with transition metal ions is an effective way to decrease the polymerization pressure. 3 The mononitrides with a trivalent rare-earth cation are reported to form simple packed structures under pressure (B1, B2, B10) [18][19][20] with a suggested formal oxidation state configuration M 3+ N 3− , resulting in small to wide band-gap semiconductors. 21 On the contrary, several valence configurations have been proposed 22 to explain the nature of the nitrogen chemical bonding and its relation to the physical properties of MN 2 materials.…”