Ground state structures of tantalum tetraboride and triboride: an ab initio study

Abstract

Tantalum-boron compounds, which are potential candidates for superhard multifunctional materials, may possess multiple stoichiometries and structures under pressure. Using first-principle methods, ground-state TaB3 with the monoclinic C2/m space group and high-pressure TaB4 with the orthorhombic Amm2 space group have been found. They are more stable than the previously proposed structures. High-pressure boron-rich Amm2-TaB4 can be quenched to ambient pressure. The ground-state C2/m-TaB3 and high-pressure Amm2-TaB4 are two potential ultra-incompressible and hard materials with a calculated hardness of 17.02 GPa and 30.02 GPa at ambient pressure, respectively. Detailed electronic structure and chemical bonding analysis proved that the high hardness value of Amm2-TaB4 mainly stems from the strong covalent boron-boron bonds in graphene-like B layers as well as B-B bonds between layers.

Pressure-Stabilized Superconductive Ionic Tantalum Hydrides

“…Tantalum, a group 5 element, is of fundamental interest due to its superconducting properties, − and many aspects of tantalum and its compounds have been studied in depth. , In recent decades, several stoichiometries of tantalum hydrides have been investigated at ambient pressure. Asano et al reported that tantalum hydrides form an interstitial solid solution of hydrogen in tantalum over a wide composition range, and nine phases of Ta–H compounds were reported by Schober et al Simonović et al synthesized tantalum hydrides of various compositions by equilibrating tantalum with hydrogen in the temperature range 573–823 K under a constant hydrogen pressure of 1 bar .…”

Phase transition and electronic properties of Co–As binary compounds at high pressure

“…Pressure exhibits unique advantages in nding new materials, [32][33][34][35][36] thus the crystal structure and electron properties of these structures under high pressure will be examined in detail next. The full information of the initial pressure structures and phase diagrams of stable structures at different pressures are shown in ESI Fig.…”

High-Pressure Synthesis of β-Ir4B5and Determination of the Compressibility of Various Iridium Borides

“…Numerous predictions of novel iridium borides with varying Ir:B ratio, which possibly could be synthesized under high-pressure/high-temperature conditions and are expected to show interesting mechanical properties, have been made. 10,12−14,31−34 …”

“…In contrast to the limited experimental work on borides synthesized under high-pressure conditions, various theoretical studies predicted the possible synthesis of FeB 4 , ReB 4 , TaB 4 , IrB 2 , and IrB 4 , among others, under high-pressure conditions. − Specifically, the existence of a new iron-tetraboride FeB 4 with interesting physical properties like outstanding hardness and superconductivity was originally predicted by Kolmogorov et al and Bialon et al, who suggested that FeB 4 could be synthesized under high-pressure conditions. In 2014, Gou et al successfully synthesized FeB 4 under high-pressure conditions at a pressure of 15 GPa and a temperature of 1573 K .…”

“…Rau et al and Latini et al investigated the hardness of Ir 4 B 5+ x (formerly IrB 1.35 ) and Ir 5 B 4+ x (formerly IrB 1.1 ) and discovered that very thin films of both phases show a high hardness of 49.8 at a load of 0.49 N for Ir 4 B 5+ x and 43 GPa at 0.49 for Ir 5 B 4+ x . , With the exception of the hardness of those phases, very little is known about other properties, such as compressibility, of the iridium borides. Numerous predictions of novel iridium borides with varying Ir:B ratio, which possibly could be synthesized under high-pressure/high-temperature conditions and are expected to show interesting mechanical properties, have been made. ,− ,− …”