Almost all solids have regular molecule, ion, or atom arrays {crystal}|.
types
Crystals {cubic crystal} can have eight atoms around small atom, three perpendicular four-fold same-length axes, and five crystal classes.
Crystals {rhomboid crystal} can have twelve atoms around similar size atom with every third layer directly above another.
Crystals {rhombohedral crystal} can have one three-fold axis, with one axis perpendicular to the other two but with different length, and two axes with same length at 120-degree angle to perpendicular axis, and make five crystal classes.
Crystals {hexagonal crystal} {hexagon crystal} can have twelve atoms around similar size atom with alternate layers directly above each other.
Crystals {tetrahedral crystal} {tetrahedron crystal} can have four large ions around each small ion.
Crystals {octahedral crystal} {octahedron crystal} can have six large ions around each small ion.
Crystals {triangular crystal} can have three large ions around each small ion.
Crystals {planar crystal} can have two large ions around each small ion.
symmetry
Only one, two, three, four, or six rotational symmetries can fill all space with no gaps or overlaps, so only seven crystal types are common.
packing
The more similar in size atoms or ions are, the more atoms or ions can surround one atom or ion. Number of atoms or ions surrounding one atom also depends on ion charge or covalent-bond number.
lattice
Crystals have lattice structure. Including crystal type and lattice type, 32 crystal classes exist. 14 unit cell and 32 crystal class translations and transformations make 234 possible crystal shapes.
crystal growth
Crystals grow at dislocations, because binding molecules can contact two surface atoms. Impurities, long bond lengths during fast growth, and screw dislocations can cause dislocations and irregularities.
Small crystal faces grow fastest by deposition. Large crystal faces can adsorb other materials.
Crystal surfaces are never flat but are lumpy. Perfect crystals cannot grow.
Physical Sciences>Chemistry>Inorganic>Phase>Phases>Solid>Crystal
5-Chemistry-Inorganic-Phase-Phases-Solid-Crystal
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Date Modified: 2022.0224