Na4Eu2SiP4 is alpha Pu-derived structured and 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(4), and two equivalent P(3) atoms. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to one P(3), one P(4), and two equivalent P(2) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one P(3), one P(4), and two equivalent P(1) 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 Eu sites. In the first Eu site, Eu(1) is bonded in a 5-coordinate geometry to one P(1), one P(2), one P(4), and two equivalent P(3) atoms. In the second Eu site, Eu(2) is bonded in a 5-coordinate geometry to one P(4), two equivalent P(1), and two equivalent P(2) atoms. Si(1) is bonded in a distorted tetrahedral geometry to one Na(1), 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 7-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Eu(1), one Eu(2), and one Si(1) atom. In the second P site, P(1) is bonded in a 8-coordinate geometry to one Na(1), one Na(4), two equivalent Na(3), one Eu(1), two equivalent Eu(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(2), one Eu(1), two equivalent Eu(2), and one Si(1) atom. In the fourth P site, P(3) is bonded in a 8-coordinate geometry to one Na(2), one Na(3), one Na(4), two equivalent Na(1), two equivalent Eu(1), and one Si(1) atom.
Na4Eu2SiP4 is alpha Pu-derived structured and 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(4), and two equivalent P(3) atoms. The Na(1)-Si(1) bond length is 3.22 Å. The Na(1)-P(1) bond length is 3.25 Å. The Na(1)-P(2) bond length is 3.05 Å. The Na(1)-P(4) bond length is 3.05 Å. There is one shorter (3.03 Å) and one longer (3.24 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), one P(4), and two equivalent P(2) atoms. The Na(2)-P(3) bond length is 2.88 Å. The Na(2)-P(4) bond length is 3.14 Å. There is one shorter (2.93 Å) and one longer (2.98 Å) Na(2)-P(2) bond length. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one P(3), one P(4), and two equivalent P(1) atoms. The Na(3)-P(3) bond length is 2.85 Å. The Na(3)-P(4) bond length is 3.07 Å. There is one shorter (2.96 Å) and one longer (2.99 Å) Na(3)-P(1) 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 3.00 Å. The Na(4)-P(2) bond length is 2.93 Å. The Na(4)-P(3) bond length is 2.94 Å. The Na(4)-P(4) bond length is 3.16 Å. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 5-coordinate geometry to one P(1), one P(2), one P(4), and two equivalent P(3) atoms. The Eu(1)-P(1) bond length is 3.00 Å. The Eu(1)-P(2) bond length is 3.09 Å. The Eu(1)-P(4) bond length is 3.13 Å. There is one shorter (2.99 Å) and one longer (3.14 Å) Eu(1)-P(3) bond length. In the second Eu site, Eu(2) is bonded in a 5-coordinate geometry to one P(4), two equivalent P(1), and two equivalent P(2) atoms. The Eu(2)-P(4) bond length is 2.99 Å. There is one shorter (3.00 Å) and one longer (3.18 Å) Eu(2)-P(1) bond length. There is one shorter (2.98 Å) and one longer (3.11 Å) Eu(2)-P(2) bond length. Si(1) is bonded in a distorted tetrahedral geometry to one Na(1), one P(1), one P(2), one P(3), and one P(4) atom. The Si(1)-P(1) bond length is 2.31 Å. The Si(1)-P(2) bond length is 2.34 Å. The Si(1)-P(3) bond length is 2.28 Å. The Si(1)-P(4) bond length is 2.32 Å. There are four inequivalent P sites. In the first P site, P(4) is bonded in a 7-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Eu(1), one Eu(2), and one Si(1) atom. In the second P site, P(1) is bonded in a 8-coordinate geometry to one Na(1), one Na(4), two equivalent Na(3), one Eu(1), two equivalent Eu(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(2), one Eu(1), two equivalent Eu(2), and one Si(1) atom. In the fourth P site, P(3) is bonded in a 8-coordinate geometry to one Na(2), one Na(3), one Na(4), two equivalent Na(1), two equivalent Eu(1), and one Si(1) atom.