Structural transition and volume compression of CeBi up to 20 GPa

2014 The compression curve of CeBi up to 20 GPa was measured at room temperature by x-ray diffraction in a diamond anvil cell. Below 13 GPa, CeBi maintains its cubic structure of the NaCl-type with a bulk modulus B0 = 49.6 GPa, smaller than that reported for LaBi (B0 = 55 GPa). This anomalous lowering is attributed to a continuous increase of the cerium valence. At P = 13 GPa, CeBi undergoes a crystallographic transition. Two high pressure structures with close unit-cell volumes have been found to coexist : a tetragonal structure (space group P 4/m m m, Z = 1) and a cubic structure of the CsCl-type. The bulk moduli of the high pressure phases are markedly higher than that of the NaCl-type phase. The small volume change at the crystallographic transition is attributed to a decrease of the cerium valence or a lowering of the p-f mixing due to the larger cerium-bismuth distances in both high pressure phases. J. Physique 46 (1985) 889-894 JUIN 1985,