Radial distribution studies of amorphous Fe–W and Ni–P at high pressure

The procedure for the determination of a radial distribution function of an amorphous material contained in a diamond anvil pressure cell is discussed. The details of the method of computation are presented, and the results for two amorphous metals, Fe–W (72 at. % Fe) and Ni–P (75 at. % Ni), are presented and critically discussed. For the reduced structure function and its Fourier transform, the differential radial distribution function, amplitudes are not well determined, and maxima and minima are located with an absolute accuracy not better than 3%. However, for a single experimental configuration and sample, the relative changes in the first neighbor distance as a function of pressure are readily detectable, even for variations on the order of 0.5%. Measurements at 0, 0.3, 3.6, 7.5, and 10.5 GPa and room temperature indicate that Fe–W (72 at. % Fe) has a bulk modulus of about 170 GPa and has a volume compression of about 6% at 10.5 GPa. Measurements at 0.15, 2.80, and 5.50 GPa indicate that Ni–P (75 at. %Ni) has a bulk modulus of about 370 GPa at room temperature and has a volume compression of about 1.5% at 5.50 GPa.