Materials Data on KHfMg6O7 by Materials Project
KMg6HfO7 crystallizes in the tetragonal P4mm space group. The structure is two-dimensional and consists of one KMg6HfO7 sheet oriented in the (0, 0, 1) direction. K is bonded in a 8-coordinate geometry to eight O atoms. There are four shorter (2.87 Å) and four longer (2.95 Å) K–O bond lengths. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded to five O atoms to form a mixture of edge and corner-sharing MgO5 square pyramids. There are one shorter (1.98 Å) and four longer (2.10 Å) Mg–O bond lengths. In the second Mg site, Mg is bonded to five O atoms to form a mixture of distorted edge and corner-sharing MgO5 square pyramids. There are one shorter (2.08 Å) and four longer (2.11 Å) Mg–O bond lengths. In the third Mg site, Mg is bonded in a single-bond geometry to one O atom. The Mg–O bond length is 2.08 Å. In the fourth Mg site, Mg is bonded to five O atoms to form a mixture of distorted edge and corner-sharing MgO5 trigonal bipyramids. There are a spread of Mg–O bond distances ranging from 2.02–2.13 Å. Hf is bonded in a 5-coordinate geometry to five O atoms. There are one shorter (1.91 Å) and four longer (2.11 Å) Hf–O bond lengths. There are five inequivalent O sites. In the first O site, O is bonded to five Mg atoms to form distorted corner-sharing OMg5 trigonal bipyramids. In the second O site, O is bonded in a distorted single-bond geometry to four equivalent K and one Hf atom. In the third O site, O is bonded in a 5-coordinate geometry to five Mg atoms. In the fourth O site, O is bonded in a 3-coordinate geometry to two equivalent K, one Mg, and two equivalent Hf atoms. In the fifth O site, O is bonded to five Mg atoms to form a mixture of distorted edge and corner-sharing OMg5 square pyramids.