The dependences of the elastic stiffness moduli and the Poisson ratio of natural iron pyrites FeS2upon pressure and temperature

The hydrostatic pressure and temperature dependence of velocities of ultrasonic modes propagated in natural crystals of iron pyrites FeS 2 have been measured. It is confirmed that C 12 is positive; the Poisson ratio shows the usual positive sign; it becomes more positive under pressure and remains positive down to low temperatures. Vibrational anharmonicity of iron pyrites is discussed in the Gruneisen parameter approach.