PHOTON SPECTRA, INTERATOMIC INTERACTION POTENTIALS AND SIMULATION OF LATTICE-DEFECTS IN IRIDIUM AND RHODIUM

The method of inelastic neutron scattering has been used to measure th e frequencies of the transverse branch of phonons in Ir in the <001> a nd <110> directions. The results obtained are used to fit the interato mic interaction potential PHI(r) for Ir, which describes with high acc uracy the Ir lattice properties, including energy characteristics of p oint defects. The analogous potential is plotted for Rh. Specific feat ures of PHI(r) in Ir and Rh are discussed; in particular, 'rigidity' a t small distances and weakly pronounced Friedel oscillations. Elastic properties, phonon spectra, the formation energies of vacancies, inter stitial atoms, and stacking faults, as well as the migration energies of vacancies, and interstitial atoms in Ir and Rh, are calculated.