C2/m-carbon: structural, mechanical, and electronic properties

Abstract

The structural, mechanical, and electronic properties of C2/m-carbon were studied utilizing the firstprinciples calculations. The calculated lattice parameters and elastic constants of diamond are in excellent agreement with the available experimental data, indicating our calculations for C2/m-carbon are valid and believable. The calculated elastic constants indicate that C2/m-carbon is mechanically stable according to the elastic stability criteria under pressure. Furthermore, the elastic anisotropy has been visualized in detail by plotting the directional dependence of Poisson's ratio, Young's modulus, and shear modulus, whereas the calculated values of Poisson's ratio and B/G present their brittle manner. B/G increases under increasing pressure with B/G = 1.75 at about 260.74 GPa and v increases observed with increasing pressure with v = 0.26 at about 261.35 GPa for C2/m-carbon, respectively. Our calculations predict that C2/m-carbon is an indirect semiconductor with wide band gap of 4.197 eV.

Structural, Electronic, and Thermodynamic Properties of Tetragonal t-SixGe3−xN4

“…It is well known that elastic anisotropy has important implications in engineering science and crystal physics. The directional dependence of the anisotropy is calculated by the elastic anisotropy measures (ELAM) [ 63 , 64 ] code. The two-dimensional (2D) representation of Poisson’s ratio v in (001), (010), (100), (101), (110), and (111) planes for t -Si x Ge 3− x N 4 ( x = 0, 1, 2, 3) alloys are shown in Figure 4 .…”

“…The maximum Poisson’s ratio for t -Si 3 N 4 , t -Si 2 GeN 4 , t -SiGe 2 N 4 , and t -Ge 3 N 4 are 0.59, 0.60, 0.62, and 0.70, respectively, following the sequence t -Si 3 N 4 > t -Si 2 GeN 4 > t -SiGe 2 N 4 > t -Ge 3 N 4 . The following directional dependence of anisotropy is usually described by vector direction ( θ , φ ), where θ ( φ ) represents the angle between the vector and the x -axis ( z -axis) positive direction, and they are expressed in radians [ 63 , 64 ]. The positions of the maximum Poisson’s ratio for t -Si 3 N 4 , t -Si 2 GeN 4 , t -SiGe 2 N 4 , and t -Ge 3 N 4 appear at θ = 0.79, φ = 0.00; θ = 2.36, φ = 0.00; θ = 1.57, φ = 3.93; and θ = 2.33, φ = 0.00, respectively.…”

A Reinvestigation of a Superhard Tetragonal sp3 Carbon Allotrope

“…The hardness of $\mathrm{normalI}\overline{4}$–carbon, C2/m–16 carbon, M carbon, c-BN and diamond is calculated by using Lyakhov and Oganov’s model [55]. The hardness of $\mathrm{normalI}\overline{4}$–carbon is 55.5 GPa, which is slightly smaller than that of C2/m–16 carbon (59.5 GPa) [12] and M carbon (66.6 GPa), approximately half of that of diamond (89.7 GPa), and slightly larger than that of c-BN (49.9 GPa); the hardness of diamond is very close to the result of Ref [55] (91.0 GPa) using the Lyakhov and Oganov’s model. The hardness of $\mathrm{normalI}\overline{4}$–carbon is 83.0 GPa in Ref [45], the main reason for this situation is that the empirical formula may over or underestimate the value of the material’s hardness.…”

“…From 0 to 100 GPa, $\mathrm{normalI}\overline{4}$–carbon is brittle; namely, the brittleness of $\mathrm{normalI}\overline{4}$–carbon decreases with increasing pressure. Compared with other carbon allotropes (P222 1 –carbon: 0.872 [13]; C2/m–16 carbon: 0.867 [12]; Imma–carbon: 0.858 [12]; diamond: 0.831 [12]), $\mathrm{normalI}\overline{4}$–carbon (0.933) has the least brittleness at ambient pressure.…”

Physical Properties of XN (X = B, Al, Ga, In) in the Pm−3n phase: First-Principles Calculations

“…Lately, a growing number of studies have been conducted in the field of novel semiconductor materials, such as III-V nitride compound [1][2][3][4][5][6][7][8][9], other III-V compound materials [13][14][15][16][17][18][19][20], carbon-based [14][15][16][17][18][19][20][21], and silicon-based [22][23][24][25][26][27][28]. The structural properties, electronic properties, mechanical attributes, and stableness of the BN polymorph in the Pnma structure were investigated, utilizing first-principles calculations by the Cambridge Serial Total Energy Package (CASTEP) plane-wave code, which was studied by Ma et al [1].…”