Pressure Dependence Investigation of the Low-Temperature Structure of TlAu(CN)2 by High-Resolution Neutron Powder Diffraction and Optical Studies

In contrast to the anomalous increase of the lattice parameter b and associated reorientation of the [Au(3)(CN)(2)](-) ion with decreasing temperature, the unit cell volume and the lattice parameters of TlAu(CN)(2) are found to decrease (at T = 62 K) linearly for external hydrostatic pressures up to 4.5 kbar. The [Au(CN)(2)](-) ions do not essentially change orientation with pressure. The structural results suggest that the change in luminescence energy with pressure is due to changes in Tl.Au as well as in Au.Au interatomic separations, which again illustrates the importance of Tl.Au covalent interactions in this compound.