Materials Data on KNaSi2O5 by Materials Project
NaKSi2O5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.64–2.84 Å. In the second K1+ site, K1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of K–O bond distances ranging from 2.66–3.23 Å. In the third K1+ site, K1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.68–2.99 Å. There are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share corners with four SiO4 tetrahedra and an edgeedge with one NaO5 trigonal bipyramid. There are a spread of Na–O bond distances ranging from 2.27–2.44 Å. In the second Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.39–2.77 Å. In the third Na1+ site, Na1+ is bonded to five O2- atoms to form distorted NaO5 trigonal bipyramids that share corners with four SiO4 tetrahedra, an edgeedge with one NaO4 tetrahedra, an edgeedge with one SiO4 tetrahedra, and an edgeedge with one NaO5 trigonal bipyramid. There are a spread of Na–O bond distances ranging from 2.33–2.56 Å. There are six inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NaO4 tetrahedra and corners with three SiO4 tetrahedra. There is one shorter (1.59 Å) and three longer (1.66 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NaO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.59–1.67 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three SiO4 tetrahedra, a cornercorner with one NaO5 trigonal bipyramid, and an edgeedge with one NaO5 trigonal bipyramid. There are a spread of Si–O bond distances ranging from 1.59–1.68 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NaO4 tetrahedra, corners with three SiO4 tetrahedra, and a cornercorner with one NaO5 trigonal bipyramid. There are a spread of Si–O bond distances ranging from 1.58–1.67 Å. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three SiO4 tetrahedra and a cornercorner with one NaO5 trigonal bipyramid. There are a spread of Si–O bond distances ranging from 1.60–1.67 Å. In the sixth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NaO4 tetrahedra, corners with three SiO4 tetrahedra, and a cornercorner with one NaO5 trigonal bipyramid. There are a spread of Si–O bond distances ranging from 1.59–1.67 Å. There are fifteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Na1+, and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one K1+, two Na1+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one K1+ and two Si4+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+ and two Si4+ atoms. In the eighth O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, two Na1+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Si4+ atoms. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to two K1+ and two Si4+ atoms. In the eleventh O2- site, O2- is bonded in a 5-coordinate geometry to two K1+, two equivalent Na1+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to one K1+, two Na1+, and one Si4+ atom. In the thirteenth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent K1+, two equivalent Na1+, and one Si4+ atom. In the fourteenth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, two Na1+, and one Si4+ atom. In the fifteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two Si4+ atoms.