Electronic structure and bonding in antimony and its high pressure phases

Abstract

The effects of pressure on the electronic structure and on the bonding properties of Sb are studied by first-principles electronic structure methods. A commensurate approximate structure is used in the calculations for the modulated incommensurate Sb-II phase. It is found that the overlap of s and p bands increases with increasing pressure resulting in pressure-induced metallization of Sb. Analyses based on the electron localization function show that there is no chemical bond between the chain atoms of a previously suggested Sb-II structure. The high total energy of this structure with respect to other structures considered is a result of the absence of this binding. Description of the structural modelsSince the Sb-II modification is a modulated incommensurate structure it has to be approximated by a commensu-

First‐ and second order Raman scattering in Sb and Bi at high pressure

“…A qualitative explanation for the behaviour of T c under pressure in the A7 structure has been given by Chen et al [26] for the case of As, for which phonon softening of the A 1g mode and an increase of the electronic density of states at the Fermi level N(E F ) have been made responsible for the observed increase Original Paper of T c as pressure rises. This explanation should hold also for Sb and Bi since theoretical studies show that N(E F ) also rises in Sb-I and Bi-I as the transitions to their high-pressure phases are approached [4][5][6][7].…”

“…Theoretical studies [4][5][6][7] indicate that these structural sequences can be understood by considering the different energetic contributions to the total energy: the A7 lattice is stabilized by the electronic band structure term, whereas the appearance of the complex monoclinic and host-guest structures is a consequence of the increasing significance of the electrostatic contributions, which finally favour the stability of the bcc lattice. Pressure tuning of the interatomic interactions affects also other properties, as can be noticed by the semimetalic to metallic transition and the appearance of superconductivity [8][9][10] under compression and is expected to affect also the lattice vibrational properties and as a consequence many thermal properties which are related to phonons.…”

First-principles electronic structure study of Sc-II

“…This suggests that host-chain interactions in Sc-II are relatively weak ͑although not negligible͒, in contrast to the situation found in Sb-II. 17 In the incommensurate phase of Sb-II chemical bonding analysis based on the electron localization function revealed the existence of chemical bonds between the chain and host atoms. The weaker coupling of the chain atoms to the host framework in the case of Sc and the fact that the chains in the two approximants have very different chain distances prompt a separate study of the effects of chain distance on the energetics.…”

Effect of pressure on the Raman modes of antimony

“…9 In the phase Sb-II, N (E F ) is much larger compared to that of Sb-I at ambient pressure. 28,29 The effect of pressure on N (E F ) of Sb-II appears to be not very pronounced. 29 So, one can speculate that a hardening of relevant phonon modes, as indicated by our Raman data for optical modes, accounts for the decrease of T c with increasing pressure in Sb-II.…”