Structural Design and Physical Properties of Gallium Nitrides under High Pressures

Abstract

Polymeric nitrogen at high pressures has been proven to be a promising candidate for the design and discovery of high-energy-density materials as well as hard materials. Here, we report predicted high-pressure structures and physical properties of gallium nitrides using an effective unbiased structure searching method combined with first-principles calculations. Several unconventional stoichiometries of GaN 2 , GaN 5 , and GaN 8 compounds were predicted to be stable at a moderate pressure. The results reveal that GaN 5 with a N content of 83.3%, which is thermodynamically stable at 62.3 GPa by squeezing solid GaN and N 2 gas, is likely to be recovered as a metastable multifunctional material at ambient pressure. Given a computed energy density of ∼3.85 kJ/g, a Vicker's hardness of ∼30 GPa, and an indirect band gap of ∼2.1 eV, GaN 5 is a potentially functional material with high-energy-density, hard, and photovoltaic properties. The present results open a new avenue to synthesize multifunctional polynitrogen compounds.

Theoretical exploration of novel boron–carbon clathrate in Sr(B,C)10 at high pressure

“…We explore the crystal structures of SrB x C 10Àx (x = 1-9) by using the CALYPSO code (Crystal structure AnaLYsis by Particle Swarm Optimization). [17][18][19] Density functional theory (DFT) calculations were performed using the Vienna ab initio simulation package (VASP), within the projector augmented wave (PAW) formalism, 20 with 4s 2 4p 6 5s 2 , 2s 2 2p 1 , and 2s 2 2p 2 electrons treated as valence states for Sr, B and C atoms, respectively. For the exchange-correlation functional, we employed the generalized gradient approximation (GGA) 21 as parameterized by Perdew, Burke, and Ernzerhof (PBE), 22 or Heyd, Scuseria and Ernzerhof (HSE06).…”

The Structural and Optical Investigation of Grown GaN Film on Porous Silicon Substrate Prepared by PLD

“…While Figure 9 b shows the refractive index of grown GaN film (n f ) that has a stable value of 0.991 in the UV region, then decreases slightly to 0.796 at 438 nm, then becomes a stable value of 0.999 as the wavelength increases. (αhυ) 2 = A(hυ-E g ) (8) hυ is the optical photon energy where h is plank's constant (6.62*10 ^-34 Joule. Sec), υ is the photon frequency, and A is constant and also named the band tailing parameter.…”

“…Furthermore, GaN has high-rise electron mobility, chemical stability, and great luminescence efficiency [7]. Moreover, GaN has thermal conductivity and high breakdown strength [8,9]. All these advantages lead to fabricating of optoelectronic devices based on GaN with high frequency/temperature and low intrinsic noise/dark current/sensitivity to ionizing radiation to play an impo rtant role in industrial, military, and space applications [10][11][12].…”

Nitrogen-rich Ce–N compounds under high pressure

“…Layered structures with an N 18 ring, N 10 ring, N 12 ring, N 10 + N 14 ring, N 22 ring, N 18 ring, and N 14 ring have been reported in K 2 N 16 , BeN 4 , GaN 5 , ScN 5 , MnN 5 , CoN 8 , and CdN 6 , respectively. 29–35 3D network structures appear in P 2 1 / c -ScN 5 . 36 Experimentally, LiN 5 , K 2 N 6 , Mg 2 N 4 , CsN 5 , and tr-BeN 4 were synthesized at 45, 45, 50, 60, and 85 GPa and can be quenched at 0, 20, 0, 18, and 0 GPa, respectively.…”