Synthesis and single-crystal X-ray diffraction characterization of ternary La-C-N and Tb-C-N solids under pressures up to 150 GPa

Ternary compounds containing carbon and nitrogen such as cyanides [CN]- and carbodiimides [CN2]2-have been known for a long time and have plenty of applications. Recently, at mild pressures (25-54 GPa) we discovered the recoverable to ambient conditions [CN3]5- anion in the series of isostructural Ln3O2(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates. The next member of this C-N anion series—ortho-nitridocarbonate [CN4]8- anion—is hitherto unknown, although its stabilization is predicted in theoretical studies and expected at higher pressures. Here, we propose a single-crystal X-ray diffraction study of La-C-N and Tb-C-N systems up to 150 GPa at ID11. The aims of the proposed experiments are a synthesis of new La-C-N and Tb-C-N solids at megabar pressure regime, characterization of their crystal chemistry and behavior upon decompression, tests of theoretical predictions, search for regularities in ternary carbonitride chemistry, and see the effect of lanthanide ion.