High Pressure and High Temperature Studies on Mercurous Chloride

Abstract

Crystals of mercurous chloride (Hg2Cl2) possess a number of unusual and interesting physical properties.1 The crystal belongs to the space group I4/mmm (D 4h 17 ).2 The structure contains chains of linear Cl-Hg-Hg-Cl molecules parallel to the c-direction. The centers of the molecules of the nearest neighbor chains are displaced c/2 along c. The structure transforms to a phase of lower symmetry at low temperature whose structure is uncertain.3,4 Richter et al.5 studied the Raman spectra of mercurous chloride at room temperature and at pressures up to 16 kbar. They report that the changes in the Raman spectra may be explained on the basis of the change of structure similar to the structure changes at low temperatures. Rosasco et al.1 found by X-ray studies that at low temperatures there is essentially no change in the value of ‘c’, whereas ‘a’ reduces considerably. Hence it is thought desirable to undertake X-ray studies on mercurous chloride at high pressures and high temperatures. This paper gives an account of the preliminary results obtained.