Crystal structures

3rd chapter

what is lattice

Regular geometrical arrangement of points in crystal space

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A lattice is the arrangement of points in the crystal structure of a crystalline solid.

Crystal structure

The manner in which atoms or ions are arrayed in space

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The crystal structure is defined in terms of the unit cell geometry and the atoms' positions within the unit cell.

crystalline

Periodic and repeating three-dimensional array of atoms, ions, or molecules

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A crystalline solid is a material with a repeating three-dimensional pattern.

Unit cell edge length for face-centered cubic

a=2R(square root 2)

coordination number

The number of atomic or ionic nearest neighbors

for sc: 6

polymorphism

The ability of a solid material to exist in more than one form or crystal structure.

allotropy

The possibility of the existence of two or more different crystal structures for a substance (generally an elemental solid).

cubic

most symmetry, all side lengths equal as are the angles

Tetragonal

the height is longer than width or length but angles are all the same

Orthorhombic

no side length is equal but angles all equal

rhombohedral

all length is equal. has no 90 degree angle but theres acute and obtose ones. the acute angles have same value and obtuse have same angle. each side depicts a diamond

monoclinic

no length is equal. some angles are 90 some are not

triclinic

all sides diff length and no angle is 90

what is linear density

number of atoms over unit length of direction vector

what is planar density

number of atoms centered on plane over area of plane

single crystal

A crystalline solid for which the periodic and repeated atomic pattern extends throughout its entirety without interruption. natural single crystals have flat faces

Grain

An individual crystal in a material

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A grain is an individual crystal in which the crystallographic orientation is the same throughout.

Grain Boundary

The interface between adjacent grains having different orientations

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The grain boundary is the interface between adjoining grains. Each adjoining grain has a different crystallographic orientation.

anisotropic

Exhibiting different values of a property in different crystallographic directions.

isotropic

Having identical values of a property in all crystallographic directions

noncrystalline

The solid state in which there is no long-range atomic order.

amorphous

Having a noncrystalline structure