Physical Properties of Group 14 in P6₂22 Phase: First-Principles Calculations*

Abstract

Two new Group IV element allotropes Si3 and Ge3 in P6222 phase are predicted in this work and their physical properties are investigated using the density functional theory. Each of the newly predicted allotropes has a superdense structure, which is mechanically, dynamically, and thermodynamically stable, as verified by elastic constants, phonon dispersion spectra and relative enthalpies, respectively. The mechanical anisotropy properties are studied in detail by illustrating the directional dependence of Young’s modulus, discussing the universal anisotropic index, and calculating shear anisotropy factors together with bulk moduli. It shows that P6222–Si3 exhibits the greater anisotropy than P6222–Ge3, and interestingly both of the newly predicted crystals appear to be isotropic in the (001) plane. Additionally, the Debye temperature, sound velocities, and the minimum thermal conductivity are examined to evaluate the thermodynamic properties of C3, Si3, and Ge3 in P6222 phase, and the electronic band structures are achieved by HSE06 hybrid functional, which indicate that P6222–C3 and –Si3 are indirect band gap semiconductors and P6222–Ge3 exhibits the metallic feature.

Designing a Novel Trigonal Silicon Material: First-Principles Calculations

“…Under normal circumstances, the bonding force between atoms is strengthened as the Debye temperature increases. Table IV (see [40,55]) shows the estimated shear wave velocity (v s ), compression wave velocity (v p ), average sound velocity (v m ), and Debye temperature Θ D of tri-Si 18 . It is noteworthy that the Debye temperature of tri-Si 18 is slightly lower than diamond-Si, as evident from the table.…”

Effect of Vacancy on Physical Properties of Cmcm Si24

“…Although more and more researchers are interested in the other allotropes and alloys [10][11][12][13][14][15][16][17], a number of researchers keep searching for silicon allotropes that have direct band gaps or excellent material properties. Through continuous efforts, the researchers predicted a lot of silicon allotropes [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34].…”

Six novel carbon and silicon allotropes with their potential application in photovoltaic field

“…Pure silicon and germanium also adopt the diamond form under natural conditions and act as semiconductor materials. In recent decades, many new carbon allotropes have been continuously predicted or synthesized [5][6][7][8][9][10][11][12] such as O-carbon [7], M-carbon [10], P2/m C 54 [11], W-carbon [12], Z-carbon [13] and carbon foam [14][15][16]. By deposition of vacuumsublimated graphite, Krainyukova et al [17] obtained a stable honeycomb carbon allotrope, which exhibits high levels of gas absorption capacity outperforming both fullerites or nanotubes.…”