Elastic neutron scattering investigations of new high-pressure phases of KCN

Two recently discovered high-pressure phases of KCN were studied with elastic neutron scattering techniques. For phase $C$ we found the space group $\mathrm{Aa}$ which is the space group of strained KCN at 165 K at zero pressure as expected, but the orientations of the C${\mathrm{N}}^{-}$ molecules follow a staggered and ordered pattern pointing in between [100] and [110] directions of the original NaCl-type structure. We determined the lattice parameters of phase $D$, of the cubic phase $\mathrm{Fm}3m$ under pressure, and of the well-known orthorhombic low-temperature phase $\mathrm{Immm}$. Our measurements excellently confirm the phase diagram of KCN which was determined earlier by Raman spectroscopy.