Structural study of FeSi2 under pressure

The structural properties of beta- and alpha-FeSi2 were examined by high-pressure x-ray diffraction at room temperature. In beta-FeSi2, the lattice compression in the longest a axis is larger than in the b and c axes. The expected pressure-induced quenching by the Jahn-Teller effect on gamma-FeSi2 was not achieved in the pressure range investigated. The bulk modulus B-0 of beta-FeSi2 and its derivative B-0(') were determined to be 243.5 GPa and 3.2 GPa, respectively. A high-pressure phase, tentatively assigned to be tetragonal, appeared at about 20 GPa. For alpha-FeSi2, a higher temperature phase of beta-FeSi2, the bulk modulus B-0 and its derivative B-0(') were determined to be 183 GPa and 6.2 GPa, respectively. The experimental values of B-0 are compared with the values estimated by various first-principles calculations, where the characteristic tendency is shown. (C) 2004 American Institute of Physics.