High-pressure metallization and amorphization of the molecular crystal Sn(IBr)(2)

An insulator-to-metal transition concurring with amorphization is found in the cubic (Pa (3) over bar) molecular crystal Sn(IBr)(2) at P approximate t o 20 GPa. Measurements were carried out with diamond-anvil cells at pressur es up to similar to 30 GPa using resistance measurements, X-ray diffraction (XRD), and Sn-119 Mossbauer spectroscopy (MS). With increasing pressure a new crystalline phase is observed in the 10-23 GPa range; at P approximate to 16 GPa, a gradual onset of structural disorder is first observed, and fu ll amorphization takes place at P greater than or equal to 23 GPa. Both ele ctronic properties as measured by R(P,T) and MS data are consistent with a gradual growth of disordered (SnI2Br2)(n) polymeric chains, formed by inter molecular I-I bonding allowing for electronic delocalization to occur. Upon decompression both XRD and Sn-119 MS show a significant pressure hysteresi s. (C) 1999 Elsevier Science B.V. All rights reserved.