Elastic and thermodynamic properties of OsSi, OsSi2 and Os2Si3

All components of the elasticity tensors for OsSi (P213), OsSi2 (Cmca) and Os2Si3 (Pbcn and P-4c2) were computed by means of the stress–strain method in the framework of the density functional theory. The total energies and stress were calculated using density functional theory within the local density and conjugate gradient approximations. From the knowledge of the elastic constants, the Born stability criteria were discussed and the Debye approximation was used to evaluate the enthalpies of formation (ΔHf) of the different compounds. The ΔHf calculated at 298 K for OsSi is in correct agreement with the experimental data but for Os2Si3(Pbcn) ΔHf is 30 kJ/mol of atoms more exothermic than the measured one. Moreover, we have found that from 1200 K the P-4c2 phase of Os2Si3 is most stable from the energy point of view than the Pbcn structure.