Materials Data on Na2SnAs2 by Materials Project

Na2SnAs2 is Spinel-like structured and crystallizes in the tetragonal I4_1/acd space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a distorted see-saw-like geometry to four As3- atoms. There are two shorter (3.10 Å) and two longer (3.31 Å) Na–As bond lengths. In the second Na1+ site, Na1+ is bonded in a rectangular see-saw-like geometry to four As3- atoms. There are a spread of Na–As bond distances ranging from 3.02–3.09 Å. In the third Na1+ site, Na1+ is bonded to four As3- atoms to form NaAs4 tetrahedra that share corners with eight equivalent SnAs4 tetrahedra and an edgeedge with one NaAs4 tetrahedra. There are two shorter (2.85 Å) and two longer (3.00 Å) Na–As bond lengths. Sn4+ is bonded to four As3- atoms to form SnAs4 tetrahedra that share corners with four equivalent NaAs4 tetrahedra and corners with four equivalent SnAs4 tetrahedra. There are a spread of Sn–As bond distances ranging from 2.64–2.69 Å. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded to four Na1+ and two equivalent Sn4+ atoms to form distorted corner-sharing AsNa4Sn2 pentagonal pyramids. In the second As3- site, As3- is bonded in a 6-coordinate geometry to four Na1+ and two equivalent Sn4+ atoms. In the third As3- site, As3- is bonded in a 6-coordinate geometry to four Na1+ and two equivalent Sn4+ atoms.