Materials Data on La2Si2O5 by Materials Project
La2Si2O5 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are two inequivalent La sites. In the first La site, La is bonded in a distorted body-centered cubic geometry to eight equivalent O atoms. All La–O bond lengths are 2.74 Å. In the second La site, La is bonded to twelve O atoms to form LaO12 cuboctahedra that share corners with four equivalent LaO12 cuboctahedra, faces with four equivalent LaO12 cuboctahedra, and faces with eight equivalent SiO5 square pyramids. There are eight shorter (2.65 Å) and four longer (2.79 Å) La–O bond lengths. Si is bonded to five O atoms to form SiO5 square pyramids that share corners with five equivalent SiO5 square pyramids and faces with four equivalent LaO12 cuboctahedra. There is one shorter (1.83 Å) and four longer (1.97 Å) Si–O bond length. There are two inequivalent O sites. In the first O site, O is bonded to four La and two equivalent Si atoms to form a mixture of face, edge, and corner-sharing OLa4Si2 octahedra. The corner-sharing octahedra tilt angles range from 0–64°. In the second O site, O is bonded in a linear geometry to four equivalent La and two equivalent Si atoms.