LaI: An Unprecedented Binary Rare Earth Metal Monohalide with a NiAs‐Type Structure

Abstract

The reduction of LaI3 with La metal at roughly 750°C proceeds via metallic LaI2 to LaI, the first halide with a hexagonal close-packed NiAs-type structure (projection along c shown on the right). This arrangement does not provide suitable interstitial sites for hydrogen atoms. The extreme c/a ratio (2.47) affords markedly strong LaLa bonding in the a,b plane. Extended Hückel band calculations suggest that LaI is a strongly anisotropic metal.