Novel Rhenium Carbides at 200 GPa

Saiana Khandarkhaeva,Vitali Prakapenka,Natalia Dubrovinskaia,Pavel Sedmak,Stella Chariton,Timofey Fedotenko,Maxim Bykov,Elena Bykova,Konstantin Glazyrin,Leonid Dubrovinsky

doi:10.1002/ejic.202000252

Abstract

Laser heating of rhenium in a diamond anvil cell to 3000±300 K at about 200 GPa results in formation of two previously unknown rhenium carbides, hexagonal WC‐type structured ReC and orthorhombic TiSi2‐type structured ReC2. The shortest C–C distances [1.758(3) Å at 219(5) GPa and 1.850(4) Å at 180(7) GPa] found in honeycomb‐like carbon nets in the structure of ReC2 are quite unusual. The Re–C solid solution formed at multimegabar pressure has the carbon content of ≈ 20 at%.

Highlights

Laser heating of rhenium in a diamond anvil cell to 3000±300 K at about 200 GPa results in formation of two previously unknown rhenium carbides, hexagonal WC-type structured ReC and orthorhombic TiSi2-type structured ReC2
The range of currently achievable static pressures has been extended to ≈ 1000 GPa due to implementation of double-stage diamond anvil cells and to ≈ 600 GPa with toroidal type anvils.[14,15,16,17]
The structures of ReC2 and ReN2[5] have nothing in common and there are no signs of formation of rhenium polycarbides with more than two carbon atoms per a formula unit at least up to 180(7) GPa and 3000 ± 300 K, unlike to the rhenium-nitrogen system.[13]

Summary

Introduction

Laser heating of rhenium in a diamond anvil cell to 3000±300 K at about 200 GPa results in formation of two previously unknown rhenium carbides, hexagonal WC-type structured ReC and orthorhombic TiSi2-type structured ReC2. We report on the in situ study of Re–C compounds formed due to chemical interactions between diamond anvils and the rhenium gasket after pulsed laser heating in DACs at about 200 GPa. The structures of all of the synthesized rhenium carbides, Re2C, ReC2, ReC, and ReC0.2 were solved and refined using single-crystal X-ray diffraction (SCXRD) providing direct and unequivocal data to judge on both the atomic arrangement and chemical composition of the crystalline matter.

Results

Conclusion