BaP2 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to two equivalent P(2), three equivalent P(1), and three equivalent P(3) atoms. In the second Ba site, Ba(2) is bonded to two equivalent P(1), two equivalent P(2), and two equivalent P(3) atoms to form BaP6 octahedra that share corners with four equivalent P(3)Ba4P2 octahedra. The corner-sharing octahedral tilt angles range from 31-81°. There are three inequivalent P sites. In the first P site, P(1) is bonded in a 6-coordinate geometry to one Ba(2), three equivalent Ba(1), one P(2), and one P(3) atom. In the second P site, P(2) is bonded in a 5-coordinate geometry to one Ba(2), two equivalent Ba(1), one P(1), and one P(3) atom. In the third P site, P(3) is bonded to one Ba(2), three equivalent Ba(1), one P(1), and one P(2) atom to form distorted PBa4P2 octahedra that share corners with two equivalent Ba(2)P6 octahedra and corners with seven equivalent P(3)Ba4P2 octahedra. The corner-sharing octahedral tilt angles range from 0-104°.
BaP2 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to two equivalent P(2), three equivalent P(1), and three equivalent P(3) atoms. There is one shorter (3.31 Å) and one longer (3.39 Å) Ba(1)-P(2) bond length. There are a spread of Ba(1)-P(1) bond distances ranging from 3.34-3.45 Å. There are two shorter (3.30 Å) and one longer (3.32 Å) Ba(1)-P(3) bond length. In the second Ba site, Ba(2) is bonded to two equivalent P(1), two equivalent P(2), and two equivalent P(3) atoms to form BaP6 octahedra that share corners with four equivalent P(3)Ba4P2 octahedra. The corner-sharing octahedral tilt angles range from 31-81°. Both Ba(2)-P(1) bond lengths are 3.30 Å. Both Ba(2)-P(2) bond lengths are 3.31 Å. Both Ba(2)-P(3) bond lengths are 3.26 Å. There are three inequivalent P sites. In the first P site, P(1) is bonded in a 6-coordinate geometry to one Ba(2), three equivalent Ba(1), one P(2), and one P(3) atom. The P(1)-P(2) bond length is 2.25 Å. The P(1)-P(3) bond length is 2.20 Å. In the second P site, P(2) is bonded in a 5-coordinate geometry to one Ba(2), two equivalent Ba(1), one P(1), and one P(3) atom. The P(2)-P(3) bond length is 2.21 Å. In the third P site, P(3) is bonded to one Ba(2), three equivalent Ba(1), one P(1), and one P(2) atom to form distorted PBa4P2 octahedra that share corners with two equivalent Ba(2)P6 octahedra and corners with seven equivalent P(3)Ba4P2 octahedra. The corner-sharing octahedral tilt angles range from 0-104°.