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Lead iodide; high pressure study; Raman spectroscopy; optical absorption

The effect of pressure on the 2H and 4H polytype of PbI₂ has been investigated by Raman and optical absorption spectroscopy, using the diamond anvil cell. The 2H-polytype undergoes pressure-induced phase transitions at 5 kbar and near 30 kbar. The 4H-polytype exhibits phase transitions near 8 kbar and above 30 kbar. The Raman modes abruptly change at these pressures. The optical absorption edge shifts red at the rate of 15±1 MeV/kbar in the 2H-PbI₂ and at the rate of 7 MeV/kbar in phase II. The latter phase is most likely to possess a 3d-structure and not a layer type. The possible structures for the high pressure phases are discussed.

A Jayaraman¹ R G Maines¹ T Chattopadhyay^{1 2}

1. AT&T Bell Laboratories, Murray Hill, New Jersey - 07974, USA
2. Centre d’Etudes Nucleaires, DRF/SPh-MDN, Grenoble, France

Published

September 1986

Manuscript received

29 April 1986