Origin of Superhardness in Icosahedral B₁₂ Materials

Abstract

Boron-rich phases with icosahedral symmetry are quite intriguing. It is important to understand the origin of hardness of boron-rich materials. By starting from a chemical bond viewpoint, a simple method for evaluating hardness of boron-rich phases is presented. This method has been applied to some materials such as R-B 12 , B 13 C 2 , and B 12 X 2 (X ) O, P, As), and the predicted hardnesses are in agreement with available experimental values. The results show that this approach provides a powerful tool for predicting superhardness when searching for novel superhard materials in boron-rich phases by first principles.

Hardness Prediction and First Principle Study of Re-123(Re = Y, Eu, Pr, Gd) Superconductors

“…[8][9][10][11] Recently, a new definition of the hardness of covalent crystals has been presented. [12][13][14][15] This paper gives a theoretical prediction of hardness values of these crystals by using the chemical bond theory of complex crystals and hardness theory. It helps to understand further the other mechanical properties.…”

First‐principles calculations of the mechanical properties of boron‐rich compounds B12N2X (X = Be, Zn, Cd)

“…The k-points of 6 × 6 × 6 were generated using the Monkhorst-Pack scheme [13] with a grid of 0.04 Å -1 . The compounds B 12 N 2 X, where X = Be, Zn, Cd, with the boron carbide (B 13 C 2 )-type structure, are built up of B 12 icosahedra linked together by N-X-N chains [8,9]. The zero-pressure single elastic constants of B 12 N 2 X (X = Be, Zn, Cd) were calculated from stress (σ) changes caused by very small strain (ε) through the relation C ij = σ i /ε j [14], as presented in Table 1.…”

“…1 Introduction Boron-rich compounds have attracted attention because of their properties such as great hardness, low density, high strength, and thermal stability, and their potential technical applications [1][2][3][4][5][6][7][8]. Recently boron-rich compounds B 12 N 2 X (X = Be, Zn, Cd) with the boron carbide-type structure have been theoretically designed and predicted to be potential superhard semiconducting materials [8,9].…”

“…Recently boron-rich compounds B 12 N 2 X (X = Be, Zn, Cd) with the boron carbide-type structure have been theoretically designed and predicted to be potential superhard semiconducting materials [8,9]. Moreover, the band gap changes with the introduction of the different metal atoms.…”

Chemical bond properties and hardness of Ca4REO(BO3)3 (RE=Sm, Gd)

“…However, mechanical properties of Ca 4 REO(BO 3 ) 3 are little investigated, although they are obviously important for all kinds of device application [7][8][9][10][11][12][13]. Therefore, this paper gives a theoretical prediction of hardness values of these crystals by using the chemical bond theory of complex crystals [14][15][16][17] and hardness theory [18][19][20][21]. It helps to further understand the other mechanical properties.…”