Sr3CaAl8 is Cubic Laves-derived structured and crystallizes in the trigonal R3m space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 12-coordinate geometry to one Sr(2), three equivalent Sr(3), three equivalent Al(2), three equivalent Al(3), and six equivalent Al(4) atoms. In the second Sr site, Sr(2) is bonded in a 16-coordinate geometry to one Sr(1), three equivalent Ca(1), three equivalent Al(1), three equivalent Al(3), and six equivalent Al(4) atoms. In the third Sr site, Sr(3) is bonded in a 16-coordinate geometry to three equivalent Sr(1), one Ca(1), three equivalent Al(2), three equivalent Al(4), and six equivalent Al(3) atoms. Ca(1) is bonded in a 16-coordinate geometry to one Sr(3), three equivalent Sr(2), three equivalent Al(1), three equivalent Al(4), and six equivalent Al(3) atoms. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to three equivalent Sr(2), three equivalent Ca(1), three equivalent Al(3), and three equivalent Al(4) atoms to form AlSr3Ca3Al6 cuboctahedra that share corners with six equivalent Al(3)Sr4Ca2Al6 cuboctahedra, corners with six equivalent Al(4)Sr5CaAl6 cuboctahedra, corners with six equivalent Al(2)Sr6Al6 cuboctahedra, edges with six equivalent Al(1)Sr3Ca3Al6 cuboctahedra, faces with nine equivalent Al(3)Sr4Ca2Al6 cuboctahedra, and faces with nine equivalent Al(4)Sr5CaAl6 cuboctahedra. In the second Al site, Al(2) is bonded to three equivalent Sr(1), three equivalent Sr(3), three equivalent Al(3), and three equivalent Al(4) atoms to form AlSr6Al6 cuboctahedra that share corners with six equivalent Al(1)Sr3Ca3Al6 cuboctahedra, corners with six equivalent Al(3)Sr4Ca2Al6 cuboctahedra, corners with six equivalent Al(4)Sr5CaAl6 cuboctahedra, edges with six equivalent Al(2)Sr6Al6 cuboctahedra, faces with nine equivalent Al(3)Sr4Ca2Al6 cuboctahedra, and faces with nine equivalent Al(4)Sr5CaAl6 cuboctahedra. In the third Al site, Al(3) is bonded to one Sr(1), one Sr(2), two equivalent Sr(3), two equivalent Ca(1), one Al(1), one Al(2), and four equivalent Al(3) atoms to form AlSr4Ca2Al6 cuboctahedra that share corners with two equivalent Al(1)Sr3Ca3Al6 cuboctahedra, corners with two equivalent Al(2)Sr6Al6 cuboctahedra, corners with four equivalent Al(3)Sr4Ca2Al6 cuboctahedra, corners with ten equivalent Al(4)Sr5CaAl6 cuboctahedra, edges with two equivalent Al(3)Sr4Ca2Al6 cuboctahedra, edges with four equivalent Al(4)Sr5CaAl6 cuboctahedra, faces with three equivalent Al(1)Sr3Ca3Al6 cuboctahedra, faces with three equivalent Al(2)Sr6Al6 cuboctahedra, faces with four equivalent Al(4)Sr5CaAl6 cuboctahedra, and faces with eight equivalent Al(3)Sr4Ca2Al6 cuboctahedra. In the fourth Al site, Al(4) is bonded to one Sr(3), two equivalent Sr(1), two equivalent Sr(2), one Ca(1), one Al(1), one Al(2), and four equivalent Al(4) atoms to form AlSr5CaAl6 cuboctahedra that share corners with two equivalent Al(1)Sr3Ca3Al6 cuboctahedra, corners with two equivalent Al(2)Sr6Al6 cuboctahedra, corners with four equivalent Al(4)Sr5CaAl6 cuboctahedra, corners with ten equivalent Al(3)Sr4Ca2Al6 cuboctahedra, edges with two equivalent Al(4)Sr5CaAl6 cuboctahedra, edges with four equivalent Al(3)Sr4Ca2Al6 cuboctahedra, faces with three equivalent Al(1)Sr3Ca3Al6 cuboctahedra, faces with three equivalent Al(2)Sr6Al6 cuboctahedra, faces with four equivalent Al(3)Sr4Ca2Al6 cuboctahedra, and faces with eight equivalent Al(4)Sr5CaAl6 cuboctahedra.
Sr3CaAl8 is Cubic Laves-derived structured and crystallizes in the trigonal R3m space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 12-coordinate geometry to one Sr(2), three equivalent Sr(3), three equivalent Al(2), three equivalent Al(3), and six equivalent Al(4) atoms. The Sr(1)-Sr(2) bond length is 3.57 Å. All Sr(1)-Sr(3) bond lengths are 3.55 Å. All Sr(1)-Al(2) bond lengths are 3.39 Å. All Sr(1)-Al(3) bond lengths are 3.43 Å. All Sr(1)-Al(4) bond lengths are 3.41 Å. In the second Sr site, Sr(2) is bonded in a 16-coordinate geometry to one Sr(1), three equivalent Ca(1), three equivalent Al(1), three equivalent Al(3), and six equivalent Al(4) atoms. All Sr(2)-Ca(1) bond lengths are 3.54 Å. All Sr(2)-Al(1) bond lengths are 3.39 Å. All Sr(2)-Al(3) bond lengths are 3.37 Å. All Sr(2)-Al(4) bond lengths are 3.39 Å. In the third Sr site, Sr(3) is bonded in a 16-coordinate geometry to three equivalent Sr(1), one Ca(1), three equivalent Al(2), three equivalent Al(4), and six equivalent Al(3) atoms. The Sr(3)-Ca(1) bond length is 3.55 Å. All Sr(3)-Al(2) bond lengths are 3.39 Å. All Sr(3)-Al(4) bond lengths are 3.44 Å. All Sr(3)-Al(3) bond lengths are 3.40 Å. Ca(1) is bonded in a 16-coordinate geometry to one Sr(3), three equivalent Sr(2), three equivalent Al(1), three equivalent Al(4), and six equivalent Al(3) atoms. All Ca(1)-Al(1) bond lengths are 3.39 Å. All Ca(1)-Al(4) bond lengths are 3.37 Å. All Ca(1)-Al(3) bond lengths are 3.38 Å. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to three equivalent Sr(2), three equivalent Ca(1), three equivalent Al(3), and three equivalent Al(4) atoms to form AlSr3Ca3Al6 cuboctahedra that share corners with six equivalent Al(3)Sr4Ca2Al6 cuboctahedra, corners with six equivalent Al(4)Sr5CaAl6 cuboctahedra, corners with six equivalent Al(2)Sr6Al6 cuboctahedra, edges with six equivalent Al(1)Sr3Ca3Al6 cuboctahedra, faces with nine equivalent Al(3)Sr4Ca2Al6 cuboctahedra, and faces with nine equivalent Al(4)Sr5CaAl6 cuboctahedra. All Al(1)-Al(3) bond lengths are 2.88 Å. All Al(1)-Al(4) bond lengths are 2.88 Å. In the second Al site, Al(2) is bonded to three equivalent Sr(1), three equivalent Sr(3), three equivalent Al(3), and three equivalent Al(4) atoms to form AlSr6Al6 cuboctahedra that share corners with six equivalent Al(1)Sr3Ca3Al6 cuboctahedra, corners with six equivalent Al(3)Sr4Ca2Al6 cuboctahedra, corners with six equivalent Al(4)Sr5CaAl6 cuboctahedra, edges with six equivalent Al(2)Sr6Al6 cuboctahedra, faces with nine equivalent Al(3)Sr4Ca2Al6 cuboctahedra, and faces with nine equivalent Al(4)Sr5CaAl6 cuboctahedra. All Al(2)-Al(3) bond lengths are 2.93 Å. All Al(2)-Al(4) bond lengths are 2.92 Å. In the third Al site, Al(3) is bonded to one Sr(1), one Sr(2), two equivalent Sr(3), two equivalent Ca(1), one Al(1), one Al(2), and four equivalent Al(3) atoms to form AlSr4Ca2Al6 cuboctahedra that share corners with two equivalent Al(1)Sr3Ca3Al6 cuboctahedra, corners with two equivalent Al(2)Sr6Al6 cuboctahedra, corners with four equivalent Al(3)Sr4Ca2Al6 cuboctahedra, corners with ten equivalent Al(4)Sr5CaAl6 cuboctahedra, edges with two equivalent Al(3)Sr4Ca2Al6 cuboctahedra, edges with four equivalent Al(4)Sr5CaAl6 cuboctahedra, faces with three equivalent Al(1)Sr3Ca3Al6 cuboctahedra, faces with three equivalent Al(2)Sr6Al6 cuboctahedra, faces with four equivalent Al(4)Sr5CaAl6 cuboctahedra, and faces with eight equivalent Al(3)Sr4Ca2Al6 cuboctahedra. There are two shorter (2.89 Å) and two longer (2.90 Å) Al(3)-Al(3) bond lengths. In the fourth Al site, Al(4) is bonded to one Sr(3), two equivalent Sr(1), two equivalent Sr(2), one Ca(1), one Al(1), one Al(2), and four equivalent Al(4) atoms to form AlSr5CaAl6 cuboctahedra that share corners with two equivalent Al(1)Sr3Ca3Al6 cuboctahedra, corners with two equivalent Al(2)Sr6Al6 cuboctahedra, corners with four equivalent Al(4)Sr5CaAl6 cuboctahedra, corners with ten equivalent Al(3)Sr4Ca2Al6 cuboctahedra, edges with two equivalent Al(4)Sr5CaAl6 cuboctahedra, edges with four equivalent Al(3)Sr4Ca2Al6 cuboctahedra, faces with three equivalent Al(1)Sr3Ca3Al6 cuboctahedra, faces with three equivalent Al(2)Sr6Al6 cuboctahedra, faces with four equivalent Al(3)Sr4Ca2Al6 cuboctahedra, and faces with eight equivalent Al(4)Sr5CaAl6 cuboctahedra. There are two shorter (2.88 Å) and two longer (2.90 Å) Al(4)-Al(4) bond lengths.