High-pressure structural evolution of the perovskite NH 4MnCl3

Abstract

The high-pressure evolution of the cubic perovskite NH4MnCl 3 has been studied in the 0-6 GPa range by angle-dispersive x-ray diffraction. A structural phase transition has been found at low pressure (PC = 0.4 GPa), in agreement with previous reports. The high-pressure phase has been refined in the tetragonal P4/mbm and orthorhombic Pbnm space groups. In either case, the structure can be described in terms of a tilted perovskite model (one tilt a0a0c+and two tilts a+b-b-, respectively). The average tilting under pressure has been estimated from the lattice parameters. The P-V relation has been fitted by a Murnaghan Equation-of-State with K0 29(2) GPa and K'0 9(1). © 2010 IOP Publishing Ltd.