First Principles Study of Rare Earth Mononitrides ScN and YN under Pressure

Abstract

We report the study of high-pressure phases of YN and ScN compounds, using a recent version of the full potential linear muffin-tin orbital (FPLMTO) method, which enables an accurate treatment of the interstitial regions. The local density approximation (LDA) was used for the exchange and correlation energy density functional. Calculations are given for lattice parameters, bulk modulus and its first derivatives in different structures. Under compression, we found that ScN transforms from NaCl-type structure (B1) to Beta-Sn-type (A5) at a pressure of around 301.3 GPa, with a direct energy gap at Γ of about 0.108 eV. This transition B1 to A5 takes place at a lower pressure than the well-known transition NaCl-type structure (B1) to CsCl-type structure (B2) (found here to be 412 GPa). Our calculations also show that YN transforms from B1 to B2 at a pressure of around 198.5 GPa.

Analysis of phase stability, elastic, electronic, thermal, and optical properties of Sc1-xYxN via ab initio methods

“…In the case of the CsCl (B2) phase, the results obtained in this paper for lattice parameter (a) are very close to the previously reported results for both binary compounds scandium nitride (ScN) and yttrium nitride (YN). However, the obtained values for bulk modulus (B) are somewhat higher as compared to theoretical results [24, 37, 39] of scandium nitride and slightly lower than the theoretical results [39,40] for previously reported results of the yttrium nitride. For alloys Sc 1-x Y x N in the CsCl phase, there are no experimental or theoretical results available in the literature for comparison.…”