LiSi2N3 is beta beryllia-derived structured and crystallizes in the orthorhombic Cmc2_1 space group. Li(1) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form LiN4 tetrahedra that share corners with two equivalent Li(1)N4 tetrahedra and corners with ten equivalent Si(1)N4 tetrahedra. Si(1) is bonded to one N(2) and three equivalent N(1) atoms to form SiN4 tetrahedra that share corners with five equivalent Li(1)N4 tetrahedra and corners with seven equivalent Si(1)N4 tetrahedra. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Li(1) and three equivalent Si(1) atoms to form NLiSi3 trigonal pyramids that share corners with five equivalent N(2)Li2Si2 tetrahedra and corners with seven equivalent N(1)LiSi3 trigonal pyramids. In the second N site, N(2) is bonded to two equivalent Li(1) and two equivalent Si(1) atoms to form distorted NLi2Si2 tetrahedra that share corners with two equivalent N(2)Li2Si2 tetrahedra and corners with ten equivalent N(1)LiSi3 trigonal pyramids.
LiSi2N3 is beta beryllia-derived structured and crystallizes in the orthorhombic Cmc2_1 space group. Li(1) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form LiN4 tetrahedra that share corners with two equivalent Li(1)N4 tetrahedra and corners with ten equivalent Si(1)N4 tetrahedra. Both Li(1)-N(1) bond lengths are 2.20 Å. There is one shorter (2.05 Å) and one longer (2.09 Å) Li(1)-N(2) bond length. Si(1) is bonded to one N(2) and three equivalent N(1) atoms to form SiN4 tetrahedra that share corners with five equivalent Li(1)N4 tetrahedra and corners with seven equivalent Si(1)N4 tetrahedra. The Si(1)-N(2) bond length is 1.68 Å. All Si(1)-N(1) bond lengths are 1.76 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Li(1) and three equivalent Si(1) atoms to form NLiSi3 trigonal pyramids that share corners with five equivalent N(2)Li2Si2 tetrahedra and corners with seven equivalent N(1)LiSi3 trigonal pyramids. In the second N site, N(2) is bonded to two equivalent Li(1) and two equivalent Si(1) atoms to form distorted NLi2Si2 tetrahedra that share corners with two equivalent N(2)Li2Si2 tetrahedra and corners with ten equivalent N(1)LiSi3 trigonal pyramids.