Structural properties, infrared reflectivity, and Raman modes of SnO at high pressure

We have investigated the high-pressure behavior of the 'lone-pair' compound SnO using monochromatic synchrotron X-ray diffraction, synchrotron far- and mid-infrared reflection measurements, and Raman spectroscopy. The litharge-type ambient pressure structure is observed up to at least 20 GPa, though with indications for a small distortion above 15 GPa. Changes in interatomic distances are determined via full Rietveld refinements of diffraction patterns. SnO is found to undergo a semiconductor to metal transition near 5(1) GPa; the transition is attributed to the closure of the indirect fundamental gap. The mode Grimeisen parameters of zone-center Raman mode frequencies are reported. The results are discussed in light of related experimental and theoretical studies of structural, dynamical, and electronic properties of SnO. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.