Measurement of the sound velocity behind a shock-wave front in mixtures of iron with diamond

The side rarefaction method was used to measure the sound velocities in pressed samples of 90/10 iron/diamond, 85/15 iron/diamond, and 90/10 iron/sulfur mixtures and in samples of pressed iron (without additives) and St.3 steel. The measurement data were compared to geophysical data with a view to find a light chemical element (or elements) in the Earth's core composition that would reduce the total density of the core compared to an iron–nickel mixture without considerably reducing the sound velocity in the core compared to a pure iron–nickel mixture at the pressures occurring in the core. It was established that the addition of diamond results in an increase in the sound velocity in shock-compressed samples and a decrease in their density compared to the other samples; therefore, in simulations of the composition of the Earth's inner layers, it is necessary take into account the possible effect of carbon in the diamond phase.