High-Pressure Synthesis of β-Ir4B5 and Determination of the Compressibility of Various Iridium Borides

"A new iridium boride, beta-Ir4B5, was synthesized under high-pressure/high-temperature conditions of 10.5 GPa and 1500 degrees C in a multianvil press with a Walker-type module. The new modification beta-Ir4B5 crystallizes in a new structure type in the orthorhombic space group Pnma (no. 62) with the lattice parameters a = 10.772(2) angstrom, b = 2.844(1) angstrom, and c = 6.052(2) angstrom with R1 = 0.0286, wR2 = 0.0642 (all data), and Z = 2. The structure was determined by single-crystal X-ray and neutron powder diffraction on samples enriched in B-11. The compound is built up by an alternating stacking of boron and iridium layers with the sequence ABA'B'. Additionally, microcalorimetry, hardness, and compressibility measurements of the binary iridium borides alpha-Ir4B5, beta-Ir4B5, Ir5B4, hexagonal Ir4B3-x and orthorhombic Ir4B3-x were carried out and theoretical investigations based on density function theory (DFT) were employed to complement a comprehensive evaluation of structure-property relations. The incorporation of boron into the structures does not enhance the compressibility but leads to a significant reduction of the bulk moduli and elastic constants in comparison to elemental iridium.

Synthesis, Crystal Structure, and Compressibilities of Mn3−x_{3−x}Ir5_5B2+x_{2+x} (0≤x≤0.5)(0 ≤ x ≤ 0.5) and Mn2_2IrB2_2

The new ternary transition metal borides Mn$_{3‐x}$Ir$_5$B$_{2+x}$ (0≤x≤0.5) and Mn$_2$IrB$_2$ were synthesized from the elements under high temperature and high‐pressure/high‐temperature conditions. Both phases can be synthesized as powder samples in a radio‐frequency furnace in argon atmosphere. High‐pressure/high‐temperature conditions were used to grow single‐crystals. The phases represent the first ternary compounds within the system Mn–Ir–B. Mn$_{3−x}$Ir$_5$B$_{2+x}$ (0≤x≤0.5) crystallizes in the Ti$_3$Co$_5$B$_2$ structure type (P4/mbm; no. 127) with parameters a=9.332(1), c=2.896(2) Å, and Z=2. Mn$_2$IrB$_2$ crystallizes in the β‐Cr$_2$IrB$_2$ crystal structure type (Cmcm; no. 63) with parameters a=3.135(3), b=9.859(5), c=13.220(3) Å, and Z=8. The compositions of both compounds were confirmed by EDX measurements and the compressibility was determined experimentally for Mn$_{3−x}$Ir$_5$B$_{2+x}$ and by DFT calculations for Mn$_2$IrB$_2$

Compressibility, microcalorimetry, elastic properties and EELS of rhenium borides

Based on synchrotron X-ray diffraction on phase-pure samples, we revised the bulk moduli of the rhenium borides Re$_7$B$_3$ (B$_0$(Re$_7$B$_3$) = 391(5) GPa) and orthorhombic Re$_3$B (B$_0$ (orthorhombic Re$_3$B) = 393(4) GPa) and determined the bulk modulus of monoclinic Re$_3$B (B$_0$ (monoclinic Re$_3$B) = 390(3) GPa). These results agree well with the DFT calculations on the elastic properties. Microcalorimetry was employed to obtain thermodynamic data for Re$_7$B$_3$ and orthorhombic Re$_3$B and we determined C $_P$ , $_298$ (Re$_7$B$_3$) = 210(4) J/mol, $\Delta H^0_{298}$ (Re$_7$B$_3$) = 40558(400) J/mol, $S^{0}_{298}$(Re$_7$B$_3$) = 267(2) J/mol K and $\Theta_{D,298}$ (Re$_7$B$_3$) = 320(2) K, as well as $C_{p,298}$(Re$_3$B) = 86(1) J/mol, $\Delta H^0_{298}$(Re$_3$B) = 16950(170) J/mol, $\Theta_{D,298}$(Re$_3$B) = 112(1) J/mol K and (Re$_3$B) = 329(3) K. Hardness measurements were performed for Re$_7$B$_3$, which gave a Vickers hardness $H_V$(5 kgf) = 14.5(4) GPa and $H_V$(10 kgf) = 14.1(3) GPa. Electron energy loss spectroscopy (EELS) was performed on orthorhombic Re$_3$B and ReB$_2$, and the experimental spectra are well reproduced by theory in terms of their absorption edges

High-pressure synthesis of β-Ir4B5 and determination of the compressibility of various iridium borides

"A new iridium boride, beta-Ir4B5, was synthesized under high-pressure/high-temperature conditions of 10.5 GPa and 1500 degrees C in a multianvil press with a Walker-type module. The new modification beta-Ir4B5 crystallizes in a new structure type in the orthorhombic space group Pnma (no. 62) with the lattice parameters a = 10.772(2) angstrom, b = 2.844(1) angstrom, and c = 6.052(2) angstrom with R1 = 0.0286, wR2 = 0.0642 (all data), and Z = 2. The structure was determined by single-crystal X-ray and neutron powder diffraction on samples enriched in B-11. The compound is built up by an alternating stacking of boron and iridium layers with the sequence ABA'B'. Additionally, microcalorimetry, hardness, and compressibility measurements of the binary iridium borides alpha-Ir4B5, beta-Ir4B5, Ir5B4, hexagonal Ir4B3-x and orthorhombic Ir4B3-x were carried out and theoretical investigations based on density function theory (DFT) were employed to complement a comprehensive evaluation of structure-property relations. The incorporation of boron into the structures does not enhance the compressibility but leads to a significant reduction of the bulk moduli and elastic constants in comparison to elemental iridium.

High-Pressure Synthesis of β\beta-Ir4_4B5_5 and Determination of the Compressibility of Various Iridium Borides

Single-crystals of a new iridium boride modification β-Ir4B5 were obtained by a high-pressure/high-temperature experiment. The structure of the new compound was characterized via X-ray and neutron diffraction. Furthermore, measurements of the compressibility, hardness, and thermodynamical properties of the new phase as well as of various other iridium borides were carried out. Complementary theoretical investigations based on density functional theory (DFT) were employed to confirm our experimental findings

High-Pressure Synthesis of β‑Ir₄B₅ and Determination of the Compressibility of Various Iridium Borides

A new iridium boride, β-Ir₄B₅, was synthesized under high-pressure/high-temperature conditions of 10.5 GPa and 1500 °C in a multianvil press with a Walker-type module. The new modification β-Ir₄B₅ crystallizes in a new structure type in the orthorhombic space group <i>Pnma</i> (no. 62) with the lattice parameters <i>a</i> = 10.772(2) Å, <i>b</i> = 2.844(1) Å, and <i>c</i> = 6.052(2) Å with <i>R</i>1 = 0.0286, <i>wR</i>2 = 0.0642 (all data), and <i>Z</i> = 2. The structure was determined by single-crystal X-ray and neutron powder diffraction on samples enriched in ¹¹B. The compound is built up by an alternating stacking of boron and iridium layers with the sequence ABA′B′. Additionally, microcalorimetry, hardness, and compressibility measurements of the binary iridium borides α-Ir₄B₅, β-Ir₄B₅, Ir₅B₄, hexagonal Ir₄B_3–<i>x</i> and orthorhombic Ir₄B_3–<i>x</i> were carried out and theoretical investigations based on density function theory (DFT) were employed to complement a comprehensive evaluation of structure–property relations. The incorporation of boron into the structures does not enhance the compressibility but leads to a significant reduction of the bulk moduli and elastic constants in comparison to elemental iridium