Comparative Study of the High-Pressure Behavior of As, Sb, and Bi

Abstract

The high-pressure behavior of the heavier group 15 elements As, Sb, and Bi was investigated by means of ab initio density functional calculations employing pseudopotentials and a plane wave basis set. The high-pressure structural sequence of these elements is distinguished by the occurrence of the Bi-III structure, which is a complex, incommensurately modulated, host-guest structure. We approximated this structure by a supercell which reproduced the experimentally established pressure stability ranges of the host-guest structure for the different elements extremely well. With pressure we find an increasing admixture of d states (s-d hybridization) in the occupied levels of the electronic structure of As, Sb, and Bi. However, the s-d mixing remains at a low level. Thus, the emergence of a complex intermediate pressure structure cannot be explained by a pressure-induced altered valence state for these elements. Instead, it is argued that the Bi-III structure is a consequence of a delicate interplay between the electrostatic and the band energy contribution to the total energy. In the intermediate pressure range of heavier group 15 elements, both important parts of the total energy account equally for structural stability.

Metallic high-pressure modifications of main group elements

“…More recent single-crystal data indicate a pairing of the guest atoms which is even more pronounced [44]. This experimental finding is in excellent agreement with the results of a computational investigation of the bonding properties of Bi and Sb where for the fully relaxed structure a pair-formation is evidenced [80]. Finally, at pressures above 28 GPa, antimony forms a cubic body centred modification [81].…”

“…The low-pressure modification with an arsenic-type structure transforms at 2.5 GPa to the strongly distorted variant of a primitive cubic structure labelled as Bi-II [82]. Already at the slightly higher pressure of 2.8 GPa there is a structural reorganisation into the phase Bi-III which is -in contrast to the findings of earlier investigations [83][84][85] -characterized by an incommensurate crystal structure [74] with CN close to 9 [80]. The arrangement is very similar to that found for highpressure allotropes of the alkaline-earth metals strontium and barium or that of the lighter homologue antimony.…”

“…The arrangement is very similar to that found for highpressure allotropes of the alkaline-earth metals strontium and barium or that of the lighter homologue antimony. As for Sb, recent single crystal X-ray diffraction data indicate additional modulations of both host and framework atoms which leads to a quasi-pairing of the guest species [44] and this formation of pairs was confirmed independently by ab-initio density functional calculations [80]. Upon further compression, Bi-V with a cubic body centred arrangement is formed at pressures exceeding 8.0 GPa [86].…”

Effect of pressure on the Raman modes of antimony

“…51 concluded at a phase transition to the cP 1 structure at V ≤ 52Å 3 (incorrect), but found out that "the axial ratio converges to c/a √ 6 before the parameter u converges to u = 1/4" (correct). Another, more recent, calculation 28 concluded that the A7 → Sb-II transition takes place at P = 8.6 GPa, i.e. before the (hypothetical) A7 → cP 1 transformation might occur at the (calculated) pressure of P = 10.7 GPa.…”

“…6,9,28,51 An interesting problem had been the question of the existence of a cubic primitive (cP 1) structure of Sb at pressures between 6 and 9 GPa. The cP 1 structure can be viewed as a special case of A7 with u = 0.25 and c/a = √ 6.…”