(C)2AlSi5O12 is Keatite-derived structured and crystallizes in the monoclinic C2 space group. The structure consists of two acetylene molecules inside a AlSi5O12 framework. In the AlSi5O12 framework, Al(1) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form AlO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. In the third Si site, Si(3) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form corner-sharing SiO4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to two equivalent Si(2) atoms.
(C)2AlSi5O12 is Keatite-derived structured and crystallizes in the monoclinic C2 space group. The structure consists of two acetylene molecules inside a AlSi5O12 framework. In the AlSi5O12 framework, Al(1) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form AlO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. Both Al(1)-O(3) bond lengths are 1.73 Å. Both Al(1)-O(4) bond lengths are 1.73 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(4) bond length is 1.59 Å. The Si(1)-O(5) bond length is 1.63 Å. The Si(1)-O(6) bond length is 1.63 Å. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The Si(2)-O(2) bond length is 1.64 Å. The Si(2)-O(3) bond length is 1.59 Å. The Si(2)-O(5) bond length is 1.63 Å. The Si(2)-O(7) bond length is 1.63 Å. In the third Si site, Si(3) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form corner-sharing SiO4 tetrahedra. Both Si(3)-O(1) bond lengths are 1.63 Å. Both Si(3)-O(2) bond lengths are 1.63 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to two equivalent Si(2) atoms.