ELECTRONIC-STRUCTURE OF FACE-CENTERED TETRAGONAL IRON

Thin films of iron can be grown in either the bcc or fcc structure when using an appropriate substrate. Since the two lattices never match perfectly, it is to be expected that tetragonal distortions are present. Therefore, we have performed total energy calculations for face-centered tetragonal iron in both the ferromagnetic and paramagnetic states. The standard bcc and fcc structures are two special cases of the face-centered tetragonal space group. There are two minima in the total energy, one near the bcc line and one near the fcc line. The fcc minimum has the lowest total energy. Near the fcc minimum we find a region in the c-vs-a plane where our calculations have trouble converging. We associate this with the existence of a low-spin metastable state in this region. We also study the values of the magnetic moments as a function of crystal structure.