Ba3HfTa4O15 crystallizes in the monoclinic Pc space group. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(5), one O(6), one O(9), two equivalent O(1), two equivalent O(14), and two equivalent O(4) atoms. In the second Ba site, Ba(2) is bonded in a 6-coordinate geometry to two equivalent O(15), two equivalent O(2), and two equivalent O(3) atoms. In the third Ba site, Ba(3) is bonded to one O(6), one O(7), one O(8), one O(9), two equivalent O(10), two equivalent O(11), two equivalent O(12), and two equivalent O(13) atoms to form BaO12 cuboctahedra that share faces with two equivalent Ba(3)O12 cuboctahedra, faces with two equivalent Hf(1)O6 octahedra, faces with two equivalent Ta(1)O6 octahedra, faces with two equivalent Ta(2)O6 octahedra, and faces with two equivalent Ta(3)O6 octahedra. Hf(1) is bonded to one O(10), one O(12), one O(14), one O(3), and two equivalent O(6) atoms to form HfO6 octahedra that share  a cornercorner with one Ta(2)O6 octahedra,  a cornercorner with one Ta(4)O6 octahedra, corners with two equivalent Hf(1)O6 octahedra, corners with two equivalent Ta(3)O6 octahedra, and faces with two equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 4-46°. There are four inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(11), one O(13), one O(15), one O(4), and two equivalent O(7) atoms to form TaO6 octahedra that share  a cornercorner with one Ta(3)O6 octahedra,  a cornercorner with one Ta(4)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, and faces with two equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-36°. In the second Ta site, Ta(2) is bonded to one O(11), one O(12), one O(15), one O(2), and two equivalent O(8) atoms to form TaO6 octahedra that share  a cornercorner with one Hf(1)O6 octahedra,  a cornercorner with one Ta(4)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, and faces with two equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-36°. In the third Ta site, Ta(3) is bonded to one O(1), one O(10), one O(13), one O(14), and two equivalent O(9) atoms to form TaO6 octahedra that share  a cornercorner with one Ta(1)O6 octahedra,  a cornercorner with one Ta(4)O6 octahedra, corners with two equivalent Hf(1)O6 octahedra, corners with two equivalent Ta(3)O6 octahedra, and faces with two equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-46°. In the fourth Ta site, Ta(4) is bonded to one O(1), one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form TaO6 octahedra that share  a cornercorner with one Hf(1)O6 octahedra,  a cornercorner with one Ta(1)O6 octahedra,  a cornercorner with one Ta(2)O6 octahedra,  a cornercorner with one Ta(3)O6 octahedra, and corners with two equivalent Ta(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-40°. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Ta(3), and one Ta(4) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(2), one Ta(2), and one Ta(4) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(2), one Hf(1), and one Ta(4) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Ta(1), and one Ta(4) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Ba(1) and two equivalent Ta(4) atoms. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(3), and two equivalent Hf(1) atoms. In the seventh O site, O(7) is bonded in a distorted linear geometry to one Ba(3) and two equivalent Ta(1) atoms. In the eighth O site, O(8) is bonded in a distorted linear geometry to one Ba(3) and two equivalent Ta(2) atoms. In the ninth O site, O(9) is bonded in a distorted linear geometry to one Ba(1), one Ba(3), and two equivalent Ta(3) atoms. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to two equivalent Ba(3), one Hf(1), and one Ta(3) atom. In the eleventh O site, O(11) is bonded in a distorted linear geometry to two equivalent Ba(3), one Ta(1), and one Ta(2) atom. In the twelfth O site, O(12) is bonded in a distorted linear geometry to two equivalent Ba(3), one Hf(1), and one Ta(2) atom. In the thirteenth O site, O(13) is bonded in a distorted linear geometry to two equivalent Ba(3), one Ta(1), and one Ta(3) atom. In the fourteenth O site, O(14) is bonded to two equivalent Ba(1), one Hf(1), and one Ta(3) atom to form distorted corner-sharing OBa2HfTa tetrahedra. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to two equivalent Ba(2), one Ta(1), and one Ta(2) atom.
Ba3HfTa4O15 crystallizes in the monoclinic Pc space group. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(5), one O(6), one O(9), two equivalent O(1), two equivalent O(14), and two equivalent O(4) atoms. The Ba(1)-O(5) bond length is 3.10 Å. The Ba(1)-O(6) bond length is 3.07 Å. The Ba(1)-O(9) bond length is 3.17 Å. There is one shorter (2.98 Å) and one longer (3.01 Å) Ba(1)-O(1) bond length. There is one shorter (2.74 Å) and one longer (2.75 Å) Ba(1)-O(14) bond length. There is one shorter (2.98 Å) and one longer (3.01 Å) Ba(1)-O(4) bond length. In the second Ba site, Ba(2) is bonded in a 6-coordinate geometry to two equivalent O(15), two equivalent O(2), and two equivalent O(3) atoms. There is one shorter (2.85 Å) and one longer (2.86 Å) Ba(2)-O(15) bond length. There is one shorter (2.94 Å) and one longer (2.96 Å) Ba(2)-O(2) bond length. There is one shorter (2.86 Å) and one longer (2.90 Å) Ba(2)-O(3) bond length. In the third Ba site, Ba(3) is bonded to one O(6), one O(7), one O(8), one O(9), two equivalent O(10), two equivalent O(11), two equivalent O(12), and two equivalent O(13) atoms to form BaO12 cuboctahedra that share faces with two equivalent Ba(3)O12 cuboctahedra, faces with two equivalent Hf(1)O6 octahedra, faces with two equivalent Ta(1)O6 octahedra, faces with two equivalent Ta(2)O6 octahedra, and faces with two equivalent Ta(3)O6 octahedra. The Ba(3)-O(6) bond length is 2.75 Å. The Ba(3)-O(7) bond length is 2.87 Å. The Ba(3)-O(8) bond length is 2.85 Å. The Ba(3)-O(9) bond length is 2.82 Å. There is one shorter (2.78 Å) and one longer (2.80 Å) Ba(3)-O(10) bond length. There is one shorter (2.89 Å) and one longer (2.92 Å) Ba(3)-O(11) bond length. There is one shorter (2.81 Å) and one longer (2.84 Å) Ba(3)-O(12) bond length. There is one shorter (2.85 Å) and one longer (2.88 Å) Ba(3)-O(13) bond length. Hf(1) is bonded to one O(10), one O(12), one O(14), one O(3), and two equivalent O(6) atoms to form HfO6 octahedra that share  a cornercorner with one Ta(2)O6 octahedra,  a cornercorner with one Ta(4)O6 octahedra, corners with two equivalent Hf(1)O6 octahedra, corners with two equivalent Ta(3)O6 octahedra, and faces with two equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 4-46°. The Hf(1)-O(10) bond length is 2.18 Å. The Hf(1)-O(12) bond length is 2.18 Å. The Hf(1)-O(14) bond length is 2.08 Å. The Hf(1)-O(3) bond length is 2.04 Å. Both Hf(1)-O(6) bond lengths are 2.03 Å. There are four inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(11), one O(13), one O(15), one O(4), and two equivalent O(7) atoms to form TaO6 octahedra that share  a cornercorner with one Ta(3)O6 octahedra,  a cornercorner with one Ta(4)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, and faces with two equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-36°. The Ta(1)-O(11) bond length is 2.05 Å. The Ta(1)-O(13) bond length is 1.97 Å. The Ta(1)-O(15) bond length is 2.05 Å. The Ta(1)-O(4) bond length is 1.96 Å. There is one shorter (1.98 Å) and one longer (2.06 Å) Ta(1)-O(7) bond length. In the second Ta site, Ta(2) is bonded to one O(11), one O(12), one O(15), one O(2), and two equivalent O(8) atoms to form TaO6 octahedra that share  a cornercorner with one Hf(1)O6 octahedra,  a cornercorner with one Ta(4)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, and faces with two equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-36°. The Ta(2)-O(11) bond length is 2.06 Å. The Ta(2)-O(12) bond length is 1.96 Å. The Ta(2)-O(15) bond length is 2.00 Å. The Ta(2)-O(2) bond length is 2.00 Å. There is one shorter (1.98 Å) and one longer (2.05 Å) Ta(2)-O(8) bond length. In the third Ta site, Ta(3) is bonded to one O(1), one O(10), one O(13), one O(14), and two equivalent O(9) atoms to form TaO6 octahedra that share  a cornercorner with one Ta(1)O6 octahedra,  a cornercorner with one Ta(4)O6 octahedra, corners with two equivalent Hf(1)O6 octahedra, corners with two equivalent Ta(3)O6 octahedra, and faces with two equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-46°. The Ta(3)-O(1) bond length is 1.95 Å. The Ta(3)-O(10) bond length is 1.96 Å. The Ta(3)-O(13) bond length is 2.12 Å. The Ta(3)-O(14) bond length is 2.01 Å. There is one shorter (1.99 Å) and one longer (2.05 Å) Ta(3)-O(9) bond length. In the fourth Ta site, Ta(4) is bonded to one O(1), one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form TaO6 octahedra that share  a cornercorner with one Hf(1)O6 octahedra,  a cornercorner with one Ta(1)O6 octahedra,  a cornercorner with one Ta(2)O6 octahedra,  a cornercorner with one Ta(3)O6 octahedra, and corners with two equivalent Ta(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-40°. The Ta(4)-O(1) bond length is 2.02 Å. The Ta(4)-O(2) bond length is 1.97 Å. The Ta(4)-O(3) bond length is 1.96 Å. The Ta(4)-O(4) bond length is 2.02 Å. There is one shorter (1.91 Å) and one longer (2.12 Å) Ta(4)-O(5) bond length. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Ta(3), and one Ta(4) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(2), one Ta(2), and one Ta(4) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(2), one Hf(1), and one Ta(4) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Ta(1), and one Ta(4) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Ba(1) and two equivalent Ta(4) atoms. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(3), and two equivalent Hf(1) atoms. In the seventh O site, O(7) is bonded in a distorted linear geometry to one Ba(3) and two equivalent Ta(1) atoms. In the eighth O site, O(8) is bonded in a distorted linear geometry to one Ba(3) and two equivalent Ta(2) atoms. In the ninth O site, O(9) is bonded in a distorted linear geometry to one Ba(1), one Ba(3), and two equivalent Ta(3) atoms. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to two equivalent Ba(3), one Hf(1), and one Ta(3) atom. In the eleventh O site, O(11) is bonded in a distorted linear geometry to two equivalent Ba(3), one Ta(1), and one Ta(2) atom. In the twelfth O site, O(12) is bonded in a distorted linear geometry to two equivalent Ba(3), one Hf(1), and one Ta(2) atom. In the thirteenth O site, O(13) is bonded in a distorted linear geometry to two equivalent Ba(3), one Ta(1), and one Ta(3) atom. In the fourteenth O site, O(14) is bonded to two equivalent Ba(1), one Hf(1), and one Ta(3) atom to form distorted corner-sharing OBa2HfTa tetrahedra. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to two equivalent Ba(2), one Ta(1), and one Ta(2) atom.