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Solid state is about 3-D (sometimes 2The two-D)dimensional representations you have given are inadequate and should not be taken too seriously; crystal structure. Observation tells theory what to predict. Crystallographic 5structures are nearly always three-fold symmetry does not commonly obtain (quasicrystals)dimensional. GalliumGallium arsenide is a substituted diamond latticehas the cubic zincblende structure, shown below. Here, blue atoms can are Ga and orange atoms As (cubic)it can be the other way round, properly a zinc blende structure: too, as these atoms are related by symmetry).

enter image description hereZincblende structure
(Image source)

Shows 4x4 unit cells, blue gallium, green arsenic; each has four other kind nearest neighbors to form a tetrahedron. An internal atom counts as a whole atom,(As a wall atom as 1/2side note, an edge atom as 1/4this structure is similar to that of diamond: in diamond, both types of atoms are carbon.)

Both gallium and a corner atom as 1/8arsenic have coordination number 4; the coordination geometry is tetrahedral about both. Crystal unit cells

In fact, 5-fold symmetry is very rare in crystals (230 periodic space groups) tessellate 3-spacesee - no gaps, translationally equivalentquasicrystals for more information). 

Solid state is about 3-D (sometimes 2-D) crystal structure. Observation tells theory what to predict. Crystallographic 5-fold symmetry does not commonly obtain (quasicrystals). Gallium arsenide is a substituted diamond lattice (cubic), properly a zinc blende structure:

enter image description here

Shows 4x4 unit cells, blue gallium, green arsenic; each has four other kind nearest neighbors to form a tetrahedron. An internal atom counts as a whole atom, a wall atom as 1/2, an edge atom as 1/4, and a corner atom as 1/8. Crystal unit cells (230 periodic space groups) tessellate 3-space - no gaps, translationally equivalent.

The two-dimensional representations you have given are inadequate and should not be taken too seriously; crystal structures are nearly always three-dimensional. Gallium arsenide has the cubic zincblende structure, shown below. Here, blue atoms can are Ga and orange atoms As (it can be the other way round, too, as these atoms are related by symmetry).

Zincblende structure
(Image source)

(As a side note, this structure is similar to that of diamond: in diamond, both types of atoms are carbon.)

Both gallium and arsenic have coordination number 4; the coordination geometry is tetrahedral about both.

In fact, 5-fold symmetry is very rare in crystals (see quasicrystals for more information). 

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Solid state is about 3-D (sometimes 2-D) crystal structure. Observation tells theory what to predict. Crystallographic 5-fold symmetry does not commonly obtain (quasicrystals). Gallium arsenide is a substituted diamond lattice (cubic), properly a zinc blende structure:

Gallum arsenide unit cell http://www.pems.adfa.edu.au/~s9471553/level1/Teaching/ElectronicProperties/ZincBlende.jpg

http://phycomp.technion.ac.il/~nika/GaAs_big_big.htmlenter image description here

Shows 4x4 unit cells, blue gallium, green arsenic; each has four other kind nearest neighbors to form a tetrahedron. An internal atom counts as a whole atom, a wall atom as 1/2, an edge atom as 1/4, and a corner atom as 1/8. Crystal unit cells (230 periodic space groups) tessellate 3-space - no gaps, translationally equivalent.

Solid state is about 3-D (sometimes 2-D) crystal structure. Observation tells theory what to predict. Crystallographic 5-fold symmetry does not commonly obtain (quasicrystals). Gallium arsenide is a substituted diamond lattice (cubic), properly a zinc blende structure:

Gallum arsenide unit cell http://www.pems.adfa.edu.au/~s9471553/level1/Teaching/ElectronicProperties/ZincBlende.jpg

http://phycomp.technion.ac.il/~nika/GaAs_big_big.html

Shows 4x4 unit cells, blue gallium, green arsenic; each has four other kind nearest neighbors to form a tetrahedron. An internal atom counts as a whole atom, a wall atom as 1/2, an edge atom as 1/4, and a corner atom as 1/8. Crystal unit cells (230 periodic space groups) tessellate 3-space - no gaps, translationally equivalent.

Solid state is about 3-D (sometimes 2-D) crystal structure. Observation tells theory what to predict. Crystallographic 5-fold symmetry does not commonly obtain (quasicrystals). Gallium arsenide is a substituted diamond lattice (cubic), properly a zinc blende structure:

enter image description here

Shows 4x4 unit cells, blue gallium, green arsenic; each has four other kind nearest neighbors to form a tetrahedron. An internal atom counts as a whole atom, a wall atom as 1/2, an edge atom as 1/4, and a corner atom as 1/8. Crystal unit cells (230 periodic space groups) tessellate 3-space - no gaps, translationally equivalent.

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source | link

Solid state is about 3-D (sometimes 2-D) crystal structure. Observation tells theory what to predict. Crystallographic 5-fold symmetry does not commonly obtain (quasicrystals). Gallium arsenide is a substituted diamond lattice (cubic), properly a zinc blende structure:

Gallum arsenide unit cell http://www.pems.adfa.edu.au/~s9471553/level1/Teaching/ElectronicProperties/ZincBlende.jpg

http://phycomp.technion.ac.il/~nika/GaAs_big_big.html

Shows 4x4 unit cells, blue gallium, green arsenic; each has four other kind nearest neighbors to form a tetrahedron. An internal atom counts as a whole atom, a wall atom as 1/2, an edge atom as 1/4, and a corner atom as 1/8. Crystal unit cells (230 periodic space groups) tessellate 3-space - no gaps, translationally equivalent.