Total energy calculations were carried out by using the linear muffin-tin orbitals method, in the atomic spheres approximation, for trigonal Fei-AuSi and Fei-AgSi pairs in various charge and spin states. The calculations, which ignored lattice relaxation effects, showed that pairs with the smallest distance between the constituents had the largest binding energies. It was found that all of the neutral pairs had the minimum total energy in the lowest spin configuration of S =1/2. This was caused by a trigonal field that effectively mixed the d-states which originated from Fe, with the dangling bond hybrids from AuSi and AgSi. The hyperfine interactions which were calculated for the pairs were in reasonable agreement with experimental data.

H.Overhof, H.Weihrich: Materials Science Forum, 1995, 196-201, 1357-62