Materials Data on Na4Ca2SiAs4 by Materials Project
Na4Ca2SiAs4 crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five As3- atoms. There are a spread of Na–As bond distances ranging from 3.03–3.35 Å. In the second Na1+ site, Na1+ is bonded to four As3- atoms to form distorted NaAs4 tetrahedra that share corners with two equivalent SiAs4 tetrahedra, corners with eight NaAs4 tetrahedra, and an edgeedge with one SiAs4 tetrahedra. There are a spread of Na–As bond distances ranging from 2.91–3.11 Å. In the third Na1+ site, Na1+ is bonded to four As3- atoms to form distorted NaAs4 tetrahedra that share corners with two equivalent SiAs4 tetrahedra, corners with eight NaAs4 tetrahedra, and an edgeedge with one SiAs4 tetrahedra. There are a spread of Na–As bond distances ranging from 2.91–3.09 Å. In the fourth Na1+ site, Na1+ is bonded to four As3- atoms to form distorted NaAs4 tetrahedra that share corners with two equivalent SiAs4 tetrahedra, corners with eight NaAs4 tetrahedra, and an edgeedge with one SiAs4 tetrahedra. There are a spread of Na–As bond distances ranging from 2.99–3.12 Å. There are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 5-coordinate geometry to five As3- atoms. There are a spread of Ca–As bond distances ranging from 3.02–3.17 Å. In the second Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six As3- atoms. There are a spread of Ca–As bond distances ranging from 3.01–3.44 Å. Si4+ is bonded to four As3- atoms to form SiAs4 tetrahedra that share corners with six NaAs4 tetrahedra and edges with three NaAs4 tetrahedra. There are a spread of Si–As bond distances ranging from 2.38–2.42 Å. There are four inequivalent As3- sites. In the first As3- site, As3- is bonded in a 7-coordinate geometry to four Na1+, three Ca2+, and one Si4+ atom. In the second As3- site, As3- is bonded in a 8-coordinate geometry to four Na1+, three Ca2+, and one Si4+ atom. In the third As3- site, As3- is bonded in a 8-coordinate geometry to four Na1+, three Ca2+, and one Si4+ atom. In the fourth As3- site, As3- is bonded in a 8-coordinate geometry to five Na1+, two equivalent Ca2+, and one Si4+ atom.