Other Inorganic Compounds

This page is designed for use without the plug-in Chime. If you do have this plug-in, use the other page designed for Chime.

Click on an image to download a PDB file.

• Spinel, MgAl₂O₄
• Perovskite, CaTiO₃
• 123-Superconductor, YBa₂Cu₃O₇
• Zeolite-4A, Na₁₂[Al₁₂Si₁₂O₄₈]
• Sodium Cryptate, Na(C₁₈H₃₆N₂O₆)Na

Spinel, MgAl₂O₄

The unit cell can be regarded a single large cube assembled from 8 intermediate sized cubes. For each of the intermediate sized cubes four magnesium atoms (green) lie at half the corners and thus lie at the corners of a tetrahedron. The result is a face centered cubic arrangement of magnesium atoms throughout the large cube. Within each of the intermediate sized cubes lies a still smaller cube having sides 1/2 as long as the intermediate sized cube. The smaller cubes are of two types. One type contains a magnesium at its center surrounded by 4 tetrahedrally distributed oxygen atoms (red). The other type contains 4 oxygen and 4 aluminum atoms (gray) at its corners, with atoms of each element arranged in a tetrahedron. Since the oxygen atoms have the same arrangement and orientation in both types of smaller cube, the 32 oxygen atoms form a face centered cubic lattice.

Intermediate sized cube having inner cube of a magnesium surrounded by 4 tetrahedrally distributed oxygen atoms.

Intermediate sized cube having inner cube containing alternating oxygen and aluminum atoms at its corners.

Unit cell

For MgAl₂O₄ a=808 pm

Space group Fd3m (227)

---

Perovskite, CaTiO₃

Here the calcium ions lie at the corners of a cube. The oxygen atoms occupy the centers of the faces of the cube, and the titanium atom lies at the center. Thus the calcium ions and oxygen atoms together form a face centered cubic arrangement with the titanium atoms in one fourth of the octahedral holes (those surrounded entirely by oxygen atoms).Download PDB file.

Unit cell.

For CaTiO₃ a=536, b=764, and c=544 pm

3 unit cells.
Space group Pcmn (62)

---

123-Superconductor, YBa₂Cu₃O₇

This structure is a derivative of the perovskite structure. One formula unit of YBa₂Cu₃O₇ parallels three formula units of CaTiO₃, or Ca₃Ti₃O₉. Three Cu atoms substitute for the Ti atoms, and one Y and 2 Ba atoms take the place of the Ca atoms. The absence of eight oxygen atoms along edges (each 1/4 in the unit cell) generates the formula YBa₂Cu₃O₇.

Unit cell.

Space group Pmmm
a=382, b=389, and c=1169 pm

---

Zeolite-4A, Na₁₂[Al₁₂Si₁₂O₄₈]

Zeolites are aluminosilicates having structures characterized by cavities large enough to take up water molecules or other small molecules.Download PDB file.

A portion of the aluminosilicate network. Here all of the silicon and aluminum atoms are represented by silicon atoms (golden).

Extended structure showing only the silicon framework. (The pdb file has been adjusted to show a=90 pm instead of 123 pm in order that the graphic display shows the desired framework.)

---

Sodium Cryptate, Na(C₁₈H₃₆N₂O₆)Na

This compound contains a sodium cation surrounded by the six oxygen atoms and two nitrogen atoms of the cryptand[2,2,2]. A sodium anion completes the compound, but is not bound by the cryptand. The formula of the cryptand is N(CH₂CH₂OCH₂CH₂OCH₂CH₂]₃N.Download PDB file.

A single unit of the sodium cation surrounded by the cryptand.

Unit cell.

Space group R32 (155)
a=883; c=2926 pm

top LVC_chemistry