Undistorted linear Bi chains with hypervalent bonding in La₃TiBi₅ from single-crystal X-ray diffraction

Abstract

The crystal structure of the lanthanum titanium bismuthide LaTiBi (Pearson code hP18, Wyckoff sequence b d g2) has been established from single-crystal X-ray diffraction data and analyzed in detail using first-principles calculations. There are no anomalies pertaining to the atomic displacement parameter of the Ti site, previously reported based on a powder X-ray diffraction analysis of this compound. The anionic substructure contains columns of face-sharing TiBi octahedra and linear Bi chains. Due to a significant La(5d) and Bi(6p) orbital mixing, a perfectly one-dimensional character of the Bi chains is not realised, while a three-dimensional electronic structure is established instead. The latter fact explains the stability of the polyanionic pnictide units against Peierls distortions. The hypervalent bonding in the Bi chains is reflected in a rather long Bi-Bi distance of 3.2264 (4) Å and a typical pattern of bonding and antibonding interactions, as revealed by electronic structure calculations.

Bismuth as a Reactive Solvent in the Synthesis of Multicomponent Transition-Metal-Bearing Bismuthides

“…The apical Bi vertices of the adjacent NiBi 5 pyramids along the c direction are located at a distance of 3.199(1) Å and form zigzag chains (Figure d). Although such a long contact exceeds the expected lengths for single-bonded Bi–Bi interactions, this distance is in good agreement with reported Bi–Bi hypervalent bonds in, e.g., linear chains or oligomers. ,− The bases of the pyramids are fused to form a slightly rippled “square” net of Bi atoms (Figure e). Whereas the Bi–Bi contacts between the adjacent atoms in the net are equal, the arrangement of the Bi atoms deviates from planarity, with an atomic displacement of 0.0928(7) Å with respect to the average plane.…”

“…Both interactions are slightly underoptimized owing to population of the antibonding states just below E F . Such an electronic pattern is typical for electron-rich (hypervalent) bonding. ,, For the Bi–Bi pairs in the zigzag chains, a localized region of antibonding character is situated in the energy window of 0.7 eV < E – E F < 1.9 eV. It can be foreseen that electron doping would eventually destabilize the Bi–Bi bonding, which could lead to structural distortions or decomposition into competing phases.…”

“…The distances from the centers of the octahedra to their corners fall in the range 2.882(6)−3.067(1) Å (Table 5), in good agreement with the Ti−Bi bonds reported in other compounds. 18,19,56,57,73 Packing of the octahedra results in the emergence of short Ti−Ti and Bi−Bi contacts with d Ti−Ti = 2.9742(8)−2.9999(7) Å and d Bi−Bi = 3.347(2)−3.539(3) Å (Table 5), with the latter suggestive of hypervalent bonding. The resulting homoatomic subunits adopt pseudohexagonal symmetry and can be classified into three types: honeycomb sheets of Bi atoms, Kagome nets of Ti atoms, and a second kind of Bi honeycomb layers, which are penetrated by Bi 2 dumbbells [d Bi−Bi = 3.426(4) Å] aligned along the stacking direction (Figure 2b).…”

Synthesis, and Crystal and Electronic Structures, of the Titanium-Rich Bismuthides AE3Ti8Bi10 (AE = Sr, Ba, Eu)

“…Compositions bearing electropositive metals A , e.g., alkali, alkaline-earth, or rare-earth metals, are of particular interest, since they often show an amalgamation of metal and saltlike features, because of the significant polarization of the A – Pn bonds. Remarkable structural complexity is observed in the alkali-metal–Nb–As systems, boasting As n oligomers and mixed-valent Nb species. , Considering the heavier pnictogens Sb and Bi, many crystalline phases showing complex combinations of extended Ti–Ti and Pn – Pn bonding are known in the AE –Ti– Pn and RE –Ti– Pn systems, where AE and RE stand for alkaline-earth and rare-earth metal, respectively. − Interestingly, despite a high chemical affinity of Ti to Bi, reflected in high mutual solubility in the liquid state and the formation of several binary phases, structurally characterized multinary titanium bismuthides in the discussed systems are limited to the Heusler-type Li 3– x Ti x Bi, La 3 TiBi 5 , , displaying one-dimensional linear Bi chains and face-sharing TiBi 6 columns, and AE 5 Ti 12 Bi 19+ x ( AE = Sr, Ba, Sr+Eu) with a complex three-dimensional Ti–Bi substructure…”

A Class of Magnetic Topological Material Candidates with Hypervalent Bi Chains

“…While an extensive amount of work has been done to showcase the potential of hypervalent 2D square-nets as an avenue for new topological materials, 3,4,[45][46][47] [48][49][50][51][52][53] Density functional theory (DFT) calculations show a complex electronic structure with several band crossings at the Fermi level, some of which are gapped by SOC. Importantly, the features of a simple 1D chain model are found in the electronic structure.…”