Elastic and structural instability of cubicSn3N4andC3N4<

Abstract

We use in situ high-pressure angle dispersive x-ray diffraction measurements to determine the equation of state of cubic tin nitride ͑␥-Sn 3 N 4 ͒ under pressure up to 26 GPa. While we find no evidence for any structural phase transition, our estimate of the bulk modulus ͑B 0 ͒ is 149͑Ϯ1.2͒ GPa, much lower than the earlier theoretical estimates and that of other group IV-nitrides. We corroborate and understand these results with complementary first-principles analysis of structural, elastic, and vibrational properties of group IV-nitrides, and predict a structural transition of Sn 3 N 4 at a higher pressure of 88 GPa compared to earlier predictions of 40 GPa ͓M. Huang and Y. P. Feng, J. Appl. Phys. 96, 4015 ͑2004͔͒. Our comparative analysis of cubic nitrides shows that bulk modulus of cubic C 3 N 4 is the highest ͑379 GPa͒ while it is structurally unstable and should not exist at ambient conditions.

First-principles study of energy and atomic solubility of twinning-associated boundaries in hexagonal metals

“…Atomic-scale simulations, including molecular statics/ molecular dynamics (MS/MD) and ab initio DFT, have proved to be a valuable tool in recent decades for studying the character and stability of structural defects, and the energetic and kinetics aspects of defect nucleation, reactions and interactions [45][46][47][48][49][50]. MS/MD simulations use an empirical potential to model the interatomic forces, and have the capability of handling the motion of millions to billions of atoms on nanosecond timescales [51,52].…”

Pressure‐Tuneable Visible‐Range Band Gap in the Ionic Spinel Tin Nitride

“…Within the Fd m phase, we record the volume (Figure a) and fit a third‐order Birch–Murnaghan equation of state to derive the bulk modulus K 0 =191.8(5) GPa and pressure‐derivative K 0 ′=3.97(3). Our recorded value is 28 % larger than previous reports, but 5 % smaller than our DFT‐derived compressibility ( K 0 =201.4, K 0 ′=4.37, blue dashed line in Figure ). In the non‐hydrostatic run, deviatoric stresses meant that the Fd m phase was no longer possible to index as cubic as low as 25 GPa, although the diffraction features of the phase remained prominent and there was no evidence of a structural transition up to the highest measured pressure of 50 GPa.…”

All-electron GW quasiparticle band structures of group 14 nitride compounds

“…It is known that Si 3 N 4 can exist in two energetically favorable phases, α-and β-Si 3 N 4 , which have hexagonal crystal structures with different stacking patterns of the layered atoms perpendicular to the c axis. Since the first discovery of Si 3 N 4 in a third phase, the cubic spinel phase 8 (γ-Si 3 N 4 ) reported in 1999, this class has stimulated great research efforts in the past few years [9][10][11][12][13][14][15][16][17] . γ-Ge 3 N 4 and γ-Sn 3 N 4 have also been synthesized successfully in subsequent experiments [18][19][20] , however γ-C 3 N 4 has not yet been found experimentally.…”