  Several fcc- and hcp-structured Ir-Os alloys have been recently studied up to
30 GPa at room temperature by means of synchrotron-based X-ray powder
diffraction in diamond anvil cells. Using their bulk moduli -which increase
with increasing osmium content showing a deviation from linearity- and after
employing a thermodynamical model it was concluded that the bulk modulus for
osmium is slightly smaller than that for diamond. Here, a similar conclusion is
obtained upon employing an alternative model, thus strengthening the conclusion
that osmium is the densest but not the most incompressible element. This is
particularly interesting for Earth Sciences since it may be of key importance
towards clarifying the anomalous elastic properties of the Earth's core.
