Crystal systems describe the shape of crystal structures. By reducing the system to the smallest amount that can still be considered a crystal of that type
chemists have found there are only 7
fundamental shapes (called crystal systems). The length of the sides, and the angles that join them describes each system. Consider a simple square box. Each of the axes
length,
width, and
height, are equal and they make right angles with each other, this is
Cubic crystal system. If it is
stretched along one direction (lengthen the box) it is
Tetragonal, stretch it in two dimensions and it is
Orthorhombic. If now this badly stretched box is
skewed (
shear the top and bottom) so that the tops no longer make right angles it becomes
Monoclinic, if it is skewed again in another direction so no face is at right angle to any other it becomes
Triclinic. Ok now back to the original
cube (all sides equal, all angles equal to 90 degrees) if this cube is skewed exactly the same amount in both directions it is
Rhombohedral. Lastly if the original cube is stretched and then skewed to exactly 120 degrees then it is called
Hexagonal.
Here in a nice tabular form are the different crystal systems.
note:
1)From c programming != means not equal.
2)d = angle between b and c, e between c and a, and f between a and b.
Name: Axes: Angles(in degrees):
Cubic a=b=c d=e=f=90
Tetragonal a=b!=c d=e=f=90
Orthorhombic a!=b!=c d=e=f=90
Monoclinic a!=b!=c d=e=90 f!=90
Triclinic a!=b!=c d!=e!=f!=90
Hexagonal a=b!=c d=e=90 f=120
Rhombohedral a=b=c d=e=f!=90