Na4Sr2SiP4 crystallizes in the monoclinic Cc space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one Si(1), one P(1), one P(2), one P(3), and two equivalent P(4) atoms. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to one P(1), one P(4), and two equivalent P(3) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one P(1), one P(4), and two equivalent P(2) atoms. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one P(1), one P(2), one P(3), and one P(4) atom. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 5-coordinate geometry to one P(1), one P(2), one P(3), and two equivalent P(4) atoms. In the second Sr site, Sr(2) is bonded in a 7-coordinate geometry to one Si(1), two equivalent P(1), two equivalent P(2), and two equivalent P(3) atoms. Si(1) is bonded in a distorted tetrahedral geometry to one Na(1), one Sr(2), one P(1), one P(2), one P(3), and one P(4) atom. There are four inequivalent P sites. In the first P site, P(4) is bonded in a 8-coordinate geometry to one Na(2), one Na(3), one Na(4), two equivalent Na(1), two equivalent Sr(1), and one Si(1) atom. In the second P site, P(1) is bonded in a 7-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Sr(1), two equivalent Sr(2), and one Si(1) atom. In the third P site, P(2) is bonded in a 8-coordinate geometry to one Na(1), one Na(4), two equivalent Na(3), one Sr(1), two equivalent Sr(2), and one Si(1) atom. In the fourth P site, P(3) is bonded in a 8-coordinate geometry to one Na(1), one Na(4), two equivalent Na(2), one Sr(1), two equivalent Sr(2), and one Si(1) atom.
Na4Sr2SiP4 crystallizes in the monoclinic Cc space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one Si(1), one P(1), one P(2), one P(3), and two equivalent P(4) atoms. The Na(1)-Si(1) bond length is 3.18 Å. The Na(1)-P(1) bond length is 3.11 Å. The Na(1)-P(2) bond length is 3.20 Å. The Na(1)-P(3) bond length is 3.09 Å. There is one shorter (3.06 Å) and one longer (3.19 Å) Na(1)-P(4) bond length. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to one P(1), one P(4), and two equivalent P(3) atoms. The Na(2)-P(1) bond length is 3.09 Å. The Na(2)-P(4) bond length is 2.89 Å. There is one shorter (2.93 Å) and one longer (3.05 Å) Na(2)-P(3) bond length. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one P(1), one P(4), and two equivalent P(2) atoms. The Na(3)-P(1) bond length is 3.04 Å. The Na(3)-P(4) bond length is 2.89 Å. There is one shorter (2.91 Å) and one longer (3.01 Å) Na(3)-P(2) bond length. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one P(1), one P(2), one P(3), and one P(4) atom. The Na(4)-P(1) bond length is 3.08 Å. The Na(4)-P(2) bond length is 2.99 Å. The Na(4)-P(3) bond length is 2.91 Å. The Na(4)-P(4) bond length is 2.93 Å. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 5-coordinate geometry to one P(1), one P(2), one P(3), and two equivalent P(4) atoms. The Sr(1)-P(1) bond length is 3.18 Å. The Sr(1)-P(2) bond length is 3.07 Å. The Sr(1)-P(3) bond length is 3.10 Å. There is one shorter (3.04 Å) and one longer (3.13 Å) Sr(1)-P(4) bond length. In the second Sr site, Sr(2) is bonded in a 7-coordinate geometry to one Si(1), two equivalent P(1), two equivalent P(2), and two equivalent P(3) atoms. The Sr(2)-Si(1) bond length is 3.22 Å. There is one shorter (3.09 Å) and one longer (3.37 Å) Sr(2)-P(1) bond length. There is one shorter (3.06 Å) and one longer (3.20 Å) Sr(2)-P(2) bond length. There is one shorter (3.04 Å) and one longer (3.13 Å) Sr(2)-P(3) bond length. Si(1) is bonded in a distorted tetrahedral geometry to one Na(1), one Sr(2), one P(1), one P(2), one P(3), and one P(4) atom. The Si(1)-P(1) bond length is 2.30 Å. The Si(1)-P(2) bond length is 2.30 Å. The Si(1)-P(3) bond length is 2.34 Å. The Si(1)-P(4) bond length is 2.27 Å. There are four inequivalent P sites. In the first P site, P(4) is bonded in a 8-coordinate geometry to one Na(2), one Na(3), one Na(4), two equivalent Na(1), two equivalent Sr(1), and one Si(1) atom. In the second P site, P(1) is bonded in a 7-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Sr(1), two equivalent Sr(2), and one Si(1) atom. In the third P site, P(2) is bonded in a 8-coordinate geometry to one Na(1), one Na(4), two equivalent Na(3), one Sr(1), two equivalent Sr(2), and one Si(1) atom. In the fourth P site, P(3) is bonded in a 8-coordinate geometry to one Na(1), one Na(4), two equivalent Na(2), one Sr(1), two equivalent Sr(2), and one Si(1) atom.