Structural and magnetic properties of trigonal iron

First-principles calculations of the electronic structure of trigonal iron were performed using density-functional theory. The results are used to predict lattice spacings, magnetic moments, and elastic properties; these are in good agreement with experiment for both the bcc and fee structures. We find however, that in extracting these quantities great care must be taken in interpreting numerical fits to the calculated total energies. In addition, the results for bulk iron give insight into the properties of thin iron films. Thin films grown on substrates with mismatched lattice constants often have noncubic symmetry. If they are thicker than a few monolayers their electronic structure is similar to a bulk material with an appropriately distorted geometry, as in our trigonal calculations. We recast our bulk results in terms of an iron film grown on the (111) surface of an fee substrate, and find the predicted strain energies and moments accurately reflect the trends for iron growth on a variety of substrates.