Competition between the ionic and covalent character in the series of boron compounds BP, BAs, and BSb

Abstract

We present first-principles calculations of the bonding properties for the series of boron compounds BP, BAs, and BSb. The plane-wave pseudopotential approach to density functional theory in the local density approximation has been used to calculate the equilibrium properties, i.e., the ground-state energy, the lattice constant, the bulk modulus, its pressure derivative, and the ionicity factor. The valence electron density is used to study the modification of the bonding with respect to different pressures. The calculated electronic charge densities present an anomalous behaviour which can be characterized by reversing the standard assignments for the anion and cation in these compounds. The competition between the ionic and the covalent character in these materials is discussed in relation to the charge transfer. Estimates of the ionicity and its pressure derivative for the series of boron compounds are presented. The distribution of the valence charge density suggests that the bonding in these materials is less ionic than in other zinc-blende compounds.

Empirical study of elastic properties of BX (X = As, Sb) materials

“…As can be seen also that our value (108 GPa) of B obtained from the application of the Eq. (3) is also in excellent agreement with other available theoretical data [5][6][7], and with our previous value obtained from the relation of Eq. (2), the deviation between these two values being also about 1.11 %.…”

“…As can be seen that our calculated value (106.8 GPa) of the bulk modulus B is in excellent agreement with the previous calculation data, it′s deviates from the theoretical value (108 GPa) of the Ref. [6] by only 1.11 %. As can be seen also that our value (108 GPa) of B obtained from the application of the Eq.…”

“…The experimental bond length (d) of BSb compound can be deduced from the d-spacing (d hkl ) obtained by the authors [10]. The d-spacing obtained by the authors [10] Table 1, and compared with the previous theoretical data [5][6][7]. As can be seen that our calculated value (106.8 GPa) of the bulk modulus B is in excellent agreement with the previous calculation data, it′s deviates from the theoretical value (108 GPa) of the Ref.…”

“…(2), the deviation between these two values being also about 1.11 %. [6] 103 [7] For some A III B V materials, the homopolar energy (E h ) can be given as function of the bond length d by the following formula [13]:…”

“…They found that the electronic properties of these compounds have been features differ from those of other usual III-V materials (the direct band gap pressure coefficient is nearly independent of the anion substitutions). The BoronArsenide (BAs) material has been arousing increasing interest, both theoretically and experimentally, because of its potential inherent advantages [4][5][6].The anomalously deep-lying 2s and 2p levels have a marked effect on the ionicity of the BX (X= As, Sb) materials, they are strongly reduced (f i = 0.044 for BAs, and f i = 0.112 for BSb material) compared to other usual A III B V semiconductors [6]. The BX (X= As, Sb) materials possess also some others important characteristics such as the inverse role between the cation and the anion in terms of charge transfer [5], [7].…”