DOE OSTI2020
K(SiAs)3 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. K1+ is bonded in a 7-coordinate geometry to seven As+1.67- atoms. There are a spread of K–As bond distances ranging from 3.48–3.86 Å. There are three inequivalent Si+1.33+ sites. In the first Si+1.33+ site, Si+1.33+ is bonded in a trigonal non-coplanar geometry to three As+1.67- atoms. There are two shorter (2.41 Å) and one longer (2.43 Å) Si–As bond lengths. In the second Si+1.33+ site, Si+1.33+ is bonded in a water-like geometry to two equivalent As+1.67- atoms. Both Si–As bond lengths are 2.41 Å. In the third Si+1.33+ site, Si+1.33+ is bonded in a trigonal non-coplanar geometry to three As+1.67- atoms. There are two shorter (2.37 Å) and one longer (2.45 Å) Si–As bond lengths. There are three inequivalent As+1.67- sites. In the first As+1.67- site, As+1.67- is bonded in a 2-coordinate geometry to four equivalent K1+ and two equivalent Si+1.33+ atoms. In the second As+1.67- site, As+1.67- is bonded to two equivalent K1+ and three Si+1.33+ atoms to form distorted edge-sharing AsK2Si3 trigonal bipyramids. In the third As+1.67- site, As+1.67- is bonded in a 3-coordinate geometry to one K1+ and three Si+1.33+ atoms.