Osmium is not harder than diamond

A recent measurement found Os has a larger bulk modulus than diamond, in agreement with an earlier calculation. We have made fully relativistic linear augmented plane-wave calculations of osmium and diamond and found diamond to have the larger bulk modulus, independent of whether the local-density- or generalized-gradient-approximation (GGA) exchange-correlation potentials are used. With the GGA our bulk modulus lies between two very recent and more accurate experimental values.