Tetrahedrally Coordinated sp-Hybridized Carbon in SrCO Orthocarbonate at Ambient Conditions.

We have synthesized the orthocarbonate SrCO, in which carbon is tetrahedrally coordinated by four oxygen atoms, at moderately high pressures [20(1) GPa] and high temperatures (≈3500 K) in a diamond anvil cell by reacting a SrCO single crystal with SrO powder. We show by synchrotron powder X-ray diffraction, Raman spectroscopy, and density functional thoery calculations that this phase, and hence sp-hybridized carbon in a CO group, can be recovered at ambient conditions. The C-O bond distances are all of similar lengths [≈1.