Au with sp³ Hybridization in Li₅AuP₂

Abstract

The achievement of new bonding patterns of atoms in compounds is of great importance, which usually induces interesting physical and chemical properties. Rich oxidation states, diverse bonding types, and unique aurophilic attraction endow gold (Au) as a distinctive element. Here we report that a pressure-induced Li5AuP2, identified by a swarm intelligence-based structural prediction, becomes the first example of Au with sp3 hybridization. The most remarkable feature of Li5AuP2 is that it contains various frameworks made by AuP4, AuLi4, LiP4, and blende-like Li–P units, exhibiting noncentrosymmetry. The charge transfer from Li to Au makes Au 6p orbitals activate and hybridize with the 6s one. On the other hand, Li donating electrons to P and polar Au–P covalence make the constituent atoms satisfy the octet rule, rendering Li5AuP2 with a semiconducting character and a large second-order nonlinear optical response in the near-infrared region. Our work represents a significant step toward extending the understanding of gold chemistry.

DFT Insights into Noble Gold-Based Compound Li5AuP2: Effect of Pressure on Physical Properties

“…The interaction of Li, P, and Au at high pressure stabilizes the compounds with unique bonding patterns and features owing to the wider stoichiometry and synergetic charge transfer of ternary compounds . In that same work, Zhang et al revealed exciting properties, such as sp 3 hybridizations and bonding patterns, for the Li 5 AuP 2 compound at 25 GPa.…”

“…In the literature, it is shown that Au can acquire a 6p-element characteristic by gaining electrons from the covalent tetrahedral configuration of other atoms with an sp 3 hybridization. , It has also been reported that the reaction of Li with Au and P under high pressure leads to extraordinary negative oxidation of Au. The interaction of Li, P, and Au at high pressure stabilizes the compounds with unique bonding patterns and features owing to the wider stoichiometry and synergetic charge transfer of ternary compounds . In that same work, Zhang et al revealed exciting properties, such as sp 3 hybridizations and bonding patterns, for the Li 5 AuP 2 compound at 25 GPa.…”

“…The high oxidation states, such as +3 and + 5, are favorably affected by the expansion of the Au 5d orbital, causing the Au 6s orbital to contract. This special condition allows gold to have very high electronegativity and oxidation states; in alkali-metal aurides, this value is −1. − Additionally, under pressure, the oxidation state of gold can be expanded to higher levels+4, +6, and even beyond 3serving as a 6p-block component. , Another point is that Au features different intermolecular interactions and chemical bonding with other transition metals. Due to the aurophilic attraction between the Au + centers caused by the relativistic effect and electronic correlation of close-shell components, Au compounds offer intriguing features and a wide range of uses.…”

“…This special condition allows gold to have very high electronegativity and oxidation states; in alkali-metal aurides, this value is −1. 3 − 7 Additionally, under pressure, the oxidation state of gold can be expanded to higher levels—+4, +6, and even beyond 3—serving as a 6p-block component. 3 , 8 Another point is that Au features different intermolecular interactions and chemical bonding with other transition metals.…”

“…To the best of our knowledge, so far there has not been an attempt on such a large scale to investigate the Li 5 AuP 2 compound. Apart from finding that the compound is stable at 25 GPa, Zhang et al 7 did not mention any other information about its stability at lower pressures. To do so, in this paper, the phonon dispersion curves are calculated at lower pressures (0 to 20 GPa), leading to the detection of imaginary frequencies in the phonon dispersion up to a pressure of 18 GPa.…”