High-pressure behavior of tetragonal barium carbodiimide, BaNCN

Abstract

The high-pressure behavior of tetragonal barium carbodiimide (BaNCN) was investigated by in-situ high-pressure X-ray diffraction measurements and first-principles theoretical calculations. No phase transition or decomposition of tetragonal BaNCN was observed during compression to 6.0 GPa and subsequent decompression to ambient pressure. The bulk modulus estimated from the unit cell volume with respect to the applied pressure was 69(2) GPa, which is comparable to that estimated by first-principles calculations. The theoretical calculations indicate that contraction of the Ba-N bond length has a crucial effect on the volume change in response to pressure, whereas the C-N bonds in the NCN 2- anions remain robust against the change in pressure. • High-pressure behavior of tetragonal BaNCN was examined by synchrotron XRD and DFT calculations. • Tetragonal BaNCN exhibits a small bulk modulus of 69(2) GPa. • The large compressibility of the BaNCN originates from the contraction of Ba-N bond. • The C-N bond in NCN 2- anion is robust with respect to pressure.