X-ray study with synchrotron radiation for filled skutterudite CeRu4As12 at ambient pressure and at high pressures

Powder x-ray diffraction patterns of CeRu4As12 with synchrotron radiation have been studied at ambient pressure and at high pressures. A crystal structure of CeRu4As12 was refined by the Rietveld analysis of the powder x-ray diffraction data at ambient pressure. The thermal equivalent isotropic parameter (B-eq) of Ce in CeRu4As12 is 1.30 angstrom(2), considerably large. The large value of Beq may closely be related to the rattling effect. The volume vs. pressure curve for this arsenide has in detail been investigated at room temperature. The cell volume of CeRu4As12 decreased smoothly with increasing pressure up to 10 GPa. A bulk modulus was estimated from the volume vs. pressure curve fitted by a Birch equation of state. The bulk modulus (B-0) and its pressure derivative (B-0') of CeRu4As12 are 127 +/- 3 GPa and 5.5 +/- 9, respectively. The value of B-0 for this arsenide is smaller than that of CeRu4P12, larger than that of CeRu4Sb12. The bulk moduli of CeRu4X12 (X = P, As and Sb) decreases with increasing lattice constant.