# Crystallography

crystallographercrystallographiccrystallographicallycrystal structurecrystallographic planescrystalcrystallographerscrystallographic analysisCrystalographymathematical crystallography
Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure).wikipedia
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### Crystal structure

unit celllatticecrystal lattice
Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure).
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material.

### X-ray crystallography

X-ray diffractionprotein crystallographyX-ray
X-ray crystallography is used to determine the structure of large biomolecules such as proteins.
By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal.

### Crystal

crystallinecrystalscrystalline solid
Before the development of X-ray diffraction crystallography (see below), the study of crystals was based on physical measurements of their geometry.
The scientific study of crystals and crystal formation is known as crystallography.

### Pole figure

pole
The pole to each face is plotted on the net.
For example, pole figures in the form of stereographic projections are used to represent the orientation distribution of crystallographic lattice planes in crystallography and texture analysis in materials science.

### Goniometer

contact angle goniometerGoniometricLaser reflecting goniometer
This physical measurement is carried out using a goniometer.
In crystallography, goniometers are used for measuring angles between crystal faces.

### Crystal system

systemlattice systemcrystallographic point groups
In crystallography, the terms crystal system, crystal family, and lattice system each refer to one of several classes of space groups, lattices, point groups, or crystals.

### Miller index

Miller indices crystallographic plane
Each point is labelled with its Miller index.
Miller indices form a notation system in crystallography for planes in crystal (Bravais) lattices.

### Angstrom

Åångströmangstroms
However, the wavelength of visible light (about 4000 to 7000 ångström) is three orders of magnitude longer than the length of typical atomic bonds and atoms themselves (about 1 to 2 Å).
While deprecated by the International Bureau of Weights and Measures (BIPM) and the US National Institute of Standards and Technology (NIST), the unit is still often used in the natural sciences and technology to express sizes of atoms, molecules, microscopic biological structures, and lengths of chemical bonds, arrangement of atoms in crystals, wavelengths of electromagnetic radiation, and dimensions of integrated circuit parts.

### Cubic crystal system

cubicisometricface-centered cubic
In another example, iron transforms from a body-centered cubic (bcc) structure to a face-centered cubic (fcc) structure called austenite when it is heated.
In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube.

### Lambert azimuthal equal-area projection

Lambert azimuthal equal-areaLambert azimuthal equal areaequisolid angle
The position in 3D space of each crystal face is plotted on a stereographic net such as a Wulff net or Lambert net.
Researchers in structural geology use the Lambert azimuthal projection to plot crystallographic axes and faces, lineation and foliation in rocks, slickensides in faults, and other linear and planar features.

### Bragg's law

Bragg diffractionBragg reflectionBragg condition
Because of their highly ordered and repetitive structure, crystals give diffraction patterns of sharp Bragg reflection spots, and are ideal for analyzing the structure of solids.
The effect of the constructive or destructive interference intensifies because of the cumulative effect of reflection in successive crystallographic planes of the crystalline lattice (as described by Miller notation).

### Texture (crystalline)

textureCrystallographic preferred orientationcrystallographic texture
Such mechanisms can be studied by crystallographic texture measurements.
Texture is often represented using a pole figure, in which a specified crystallographic axis (or pole) from each of a representative number of crystallites is plotted in a stereographic projection, along with directions relevant to the material's processing history.

### Atomic packing factor

closely packed structurespacking efficiencypacking factor
In crystallography, atomic packing factor (APF), packing efficiency or packing fraction is the fraction of volume in a crystal structure that is occupied by constituent particles.

### Beevers–Lipson strip

Beevers–Lipson strips
Beevers–Lipson strips were a computational aid for early crystallographers in calculating Fourier transforms to determine the structure of crystals from crystallographic data, enabling the creation of models for complex molecules.

### Condensed matter physics

condensed matterCondensed matter theorycondensed-matter physics
A variety of topics in physics such as crystallography, metallurgy, elasticity, magnetism, etc., were treated as distinct areas until the 1940s, when they were grouped together as solid state physics.

### Crystallographic point group

crystal classcrystallographic point groupspoint group
In crystallography, a crystallographic point group is a set of symmetry operations, like rotations or reflections, that leave a central point fixed while moving the edges and faces of the crystal to the positions of features of the same size and shape.

### Crystallographic database

(Molecules need to crystallize into solids so that their regularly repeating arrangements can be taken advantage of in X-ray, neutron, and electron diffraction based crystallography.)

### Fractional coordinates

In crystallography, a fractional coordinate system is a coordinate system in which the edges of the unit cell are used as the basic vectors to describe the positions of atomic nuclei.

### International Year of Crystallography

The International Year of Crystallography (abbreviation: IYCr2014) is an event promoted in the year 2014 by the United Nations to celebrate the centenary of the discovery of X-ray crystallography and to emphasise the global importance of crystallography in human life.

### Neutron diffraction

neutronneutron crystallographydiffraction
Neutron crystallography is often used to help refine structures obtained by X-ray methods or to solve a specific bond; the methods are often viewed as complementary, as X-rays are sensitive to electron positions and scatter most strongly off heavy atoms, while neutrons are sensitive to nucleus positions and scatter strongly even off many light isotopes, including hydrogen and deuterium.
Most experiments, however, aim at the structure of crystalline solids, making neutron diffraction an important tool of crystallography.

### Mineralogy

mineralogistmineralogicalmineralogists
The modern study of mineralogy was founded on the principles of crystallography (the origins of geometric crystallography, itself, can be traced back to the mineralogy practiced in the eighteenth and nineteenth centuries) and to the microscopic study of rock sections with the invention of the microscope in the 17th century.

### Powder diffraction

X-ray powder diffractionpowder X-ray diffractionpowders
In spite of this, a certain amount of molecular information can be deduced from patterns that are generated by fibers and powders, which while not as perfect as a solid crystal, may exhibit a degree of order.

### Solid-state chemistry

solid state chemistrysolid statesolid-state
It therefore has a strong overlap with solid-state physics, mineralogy, crystallography, ceramics, metallurgy, thermodynamics, materials science and electronics with a focus on the synthesis of novel materials and their characterisation.

### Quasicrystal

quasicrystalsquasi-crystalquasicrystalline
The discovery of these aperiodic forms in nature has produced a paradigm shift in the fields of crystallography.

### Nuclear magnetic resonance crystallography

NMR crystallographyNMR crystallographic
Thus, solid-state NMR spectroscopy would be used primarily, possibly supplemented by quantum chemistry calculations (e.g. density functional theory), powder diffraction etc. If suitable crystals can be grown, any crystallographic method would generally be preferred to determine the crystal structure comprising in case of organic compounds the molecular structures and molecular packing.