Na5SiP3 is alpha Pu-derived structured and crystallizes in the monoclinic P2_1/c space group. There are five inequivalent Na sites. In the first Na site, Na(1) is bonded in a 3-coordinate geometry to one P(2), two equivalent P(1), and two equivalent P(3) atoms. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to one P(3), two equivalent P(1), and two equivalent P(2) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one P(1), one P(2), and two equivalent P(3) atoms. In the fourth Na site, Na(4) is bonded to one P(1), one P(3), and two equivalent P(2) atoms to form distorted NaP4 tetrahedra that share corners with two equivalent Na(4)P4 tetrahedra, corners with three equivalent Na(5)P4 tetrahedra, corners with three equivalent Si(1)P4 tetrahedra,  an edgeedge with one Na(5)P4 tetrahedra, and  an edgeedge with one Si(1)P4 tetrahedra. In the fifth Na site, Na(5) is bonded to one P(2), one P(3), and two equivalent P(1) atoms to form distorted NaP4 tetrahedra that share corners with three equivalent Na(4)P4 tetrahedra, corners with five equivalent Si(1)P4 tetrahedra,  an edgeedge with one Na(4)P4 tetrahedra, and  an edgeedge with one Na(5)P4 tetrahedra. Si(1) is bonded to one P(1), one P(2), and two equivalent P(3) atoms to form distorted SiP4 tetrahedra that share corners with three equivalent Na(4)P4 tetrahedra, corners with five equivalent Na(5)P4 tetrahedra,  an edgeedge with one Na(4)P4 tetrahedra, and  an edgeedge with one Si(1)P4 tetrahedra. There are three inequivalent P sites. In the first P site, P(3) is bonded in a 9-coordinate geometry to one Na(2), one Na(4), one Na(5), two equivalent Na(1), two equivalent Na(3), and two equivalent Si(1) atoms. In the second P site, P(1) is bonded in a 9-coordinate geometry to one Na(3), one Na(4), two equivalent Na(1), two equivalent Na(2), two equivalent Na(5), 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(3), one Na(5), two equivalent Na(2), two equivalent Na(4), and one Si(1) atom.
Na5SiP3 is alpha Pu-derived structured and crystallizes in the monoclinic P2_1/c space group. There are five inequivalent Na sites. In the first Na site, Na(1) is bonded in a 3-coordinate geometry to one P(2), two equivalent P(1), and two equivalent P(3) atoms. The Na(1)-P(2) bond length is 2.84 Å. There is one shorter (2.98 Å) and one longer (3.03 Å) Na(1)-P(1) bond length. There is one shorter (3.31 Å) and one longer (3.42 Å) Na(1)-P(3) bond length. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to one P(3), two equivalent P(1), and two equivalent P(2) atoms. The Na(2)-P(3) bond length is 3.02 Å. There is one shorter (2.96 Å) and one longer (3.19 Å) Na(2)-P(1) bond length. There is one shorter (3.04 Å) and one longer (3.33 Å) Na(2)-P(2) bond length. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one P(1), one P(2), and two equivalent P(3) atoms. The Na(3)-P(1) bond length is 2.95 Å. The Na(3)-P(2) bond length is 2.91 Å. There is one shorter (2.88 Å) and one longer (3.24 Å) Na(3)-P(3) bond length. In the fourth Na site, Na(4) is bonded to one P(1), one P(3), and two equivalent P(2) atoms to form distorted NaP4 tetrahedra that share corners with two equivalent Na(4)P4 tetrahedra, corners with three equivalent Na(5)P4 tetrahedra, corners with three equivalent Si(1)P4 tetrahedra,  an edgeedge with one Na(5)P4 tetrahedra, and  an edgeedge with one Si(1)P4 tetrahedra. The Na(4)-P(1) bond length is 2.89 Å. The Na(4)-P(3) bond length is 2.84 Å. There is one shorter (2.83 Å) and one longer (2.86 Å) Na(4)-P(2) bond length. In the fifth Na site, Na(5) is bonded to one P(2), one P(3), and two equivalent P(1) atoms to form distorted NaP4 tetrahedra that share corners with three equivalent Na(4)P4 tetrahedra, corners with five equivalent Si(1)P4 tetrahedra,  an edgeedge with one Na(4)P4 tetrahedra, and  an edgeedge with one Na(5)P4 tetrahedra. The Na(5)-P(2) bond length is 2.88 Å. The Na(5)-P(3) bond length is 2.90 Å. There is one shorter (2.89 Å) and one longer (3.02 Å) Na(5)-P(1) bond length. Si(1) is bonded to one P(1), one P(2), and two equivalent P(3) atoms to form distorted SiP4 tetrahedra that share corners with three equivalent Na(4)P4 tetrahedra, corners with five equivalent Na(5)P4 tetrahedra,  an edgeedge with one Na(4)P4 tetrahedra, and  an edgeedge with one Si(1)P4 tetrahedra. The Si(1)-P(1) bond length is 2.27 Å. The Si(1)-P(2) bond length is 2.25 Å. There is one shorter (2.31 Å) and one longer (2.34 Å) Si(1)-P(3) bond length. There are three inequivalent P sites. In the first P site, P(3) is bonded in a 9-coordinate geometry to one Na(2), one Na(4), one Na(5), two equivalent Na(1), two equivalent Na(3), and two equivalent Si(1) atoms. In the second P site, P(1) is bonded in a 9-coordinate geometry to one Na(3), one Na(4), two equivalent Na(1), two equivalent Na(2), two equivalent Na(5), 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(3), one Na(5), two equivalent Na(2), two equivalent Na(4), and one Si(1) atom.