Sr 3 CrN 3 : A New Electride with a Partially Filled d-Shell Transition Metal

Electrides are ionic crystals in which the electrons prefer to occupy free space, serving as anions. Because the electrons prefer to be in the pockets, channels, or layers to the atomic orbitals around the nuclei, it has been challenging to find electrides with partially filled d-shell transition metals, since an unoccupied d-shell provides an energetically favorable location for the electrons to occupy. We recently predicted the existence of electrides with partially filled d-shells using high-throughput computational screening. Here, we provide experimental support using X-ray absorption spectroscopy and X-ray and neutron diffraction to show that Sr CrN is indeed an electride despite its partial d-shell configuration. Our findings indicate that Sr CrN is the first known electride with a partially filled d-shell transition metal, in agreement with theory, which significantly broadens the criteria for the search for new electride materials.