Crystallography
Chemistry Project Synopsis by Shehryar Bilgrami
What is Crystallography?
Crystallography is a branch of chemistry that deals with finding the arrangement
and bonding of atoms in crystalline solids and with the geometric structure of
crystal lattices.
Classically, the optical properties of crystals were of value in mineralogy and
chemistry for the identification of substances. Modern crystallography is largely
based on the analysis of the diffraction of X-rays by crystals acting as optical
gratings. Using X-ray crystallography, chemists can determine the internal
structures and bonding arrangements of minerals and molecules, including the
structures of large complex molecules, such as proteins and DNA.
Max von Laue
Max Theodor Felix von Laue was a German physicist
who received the Nobel Prize in Physics in 1914 for his
discovery of the diffraction of X-rays by crystals.
In addition to his scientific endeavors with contributions
in optics, crystallography, quantum theory,
superconductivity, and the theory of relativity, Laue had
several administrative positions which advanced and
guided German scientific research and development for
four decades. A strong objector to Nazism, he was
instrumental in re-establishing and organizing German
science after World War II.
What is X-Ray Diffraction?
X-Ray diffraction can be traced back to 1912, when Max von Laue first discovered
this technique.
He discovered that X-Rays can be diffracted (the process by which a beam of light
or other system of waves is spread out because of passing through a narrow
aperture or across an edge, typically accompanied by interference between the
wave forms produced.) by crystals which led to the discovery of X-Ray
Crystallography.
This process of diffraction includes shining a beam of light through a crystal and
measuring the angles of intensities of the diffracted rays. Using these angles,
scientists can determine the positions of atoms and molecules within a crystal
lattice which can help us understand the properties of the element whose lattice is
being examined such as conductivity, optical properties melting point, boiling
point and strength.
X-rays had been discovered 17 years earlier by Roentgen but there was, at the time
of von Laue's work, no agreement on exactly what X-rays were. There was some
experimental evidence that X-rays were high energy particles (like electrons);
other data indicated that X-rays might be waves. Von Laue surmised that, if X-rays
were waves, they would have rather short wavelengths (on the order of 1 x 10-10
m) and the dimensions of the objects in crystals would be the appropriate size to
produce the phenomenon of diffraction. He exposed a crystal of copper sulfate to
X-rays and recorded the diffraction pattern on a piece of photographic
The Process of Crystallography
Using crystallography, we can study the structures and properties of structures
such as proteins and DNA too:
 Sample preparation: The first step in X-ray diffraction is to prepare a sample
of the material to be studied. The sample should be in the form of a single
crystal or a powder, depending on the type of analysis being performed.
 X-ray source: The next step is to generate a beam of X-rays using an X-ray
source, such as a synchrotron or an X-ray tube. The X-ray beam should be
monochromatic, meaning that it consists of a single wavelength of X-rays.
 Sample alignment: The sample is then aligned so that the X-ray beam is
directed onto the sample at a specific angle. The angle of incidence is
typically between 5 and 45 degrees, depending on the type of analysis being
performed.
 Diffraction pattern: When the X-ray beam strikes the sample, it is diffracted
by the atoms or molecules in the crystal lattice. The diffracted X-rays form a
diffraction pattern, which is captured by a detector.
 Data analysis: The diffraction pattern is then analyzed to determine the
atomic and molecular structure of the material. This involves measuring the
angles and intensities of the diffracted X-rays and using this information to
calculate the positions of the atoms or molecules in the crystal lattice.
 Interpretation: Finally, the results of the X-ray diffraction analysis are
interpreted to gain insights into the physical and chemical properties of the
material. This information can be used to design new materials with specific
properties for a wide range of applications.
Precautions:
Radiation safety: X-rays can be harmful to human health, so it is important to follow proper radiation safety procedures when
working with X-ray sources. This includes wearing appropriate protective gear, such as lead aprons and gloves, and ensuring that
the X-ray source is properly shielded.
Sample preparation: The sample should be prepared carefully to ensure that it is free of impurities and defects that could affect
the diffraction pattern. The sample should also be handled with care to avoid damage or contamination.
Instrument calibration: The X-ray diffraction instrument should be calibrated regularly to ensure that it is operating correctly and
produces accurate results. This includes checking the alignment of the X-ray beam, the position of the sample, and the sensitivity
of the detector.
Data analysis: The diffraction pattern should be analyzed carefully to ensure that the correct peaks are identified, and that the data
is properly processed. This includes correcting background noise and other sources of error.
https://www.nobelprize.org/prizes/physics/1914/laue/biographical/
https://it.iucr.org/Ac/itac.pdf
https://www.sciencedirect.com/topics/materials-science/x-raydiffraction#:~:text=X%2Dray%20diffraction%20(XRD),and%20physical%20prop
erties%20of%20materials.
http://macxray.chem.upenn.edu/course/intro1.html
https://www.britannica.com/science/crystallography
Other sources were used for images