Crystallography

Crystallography is the branch of science devoted to the study of molecular and crystalline structure and properties. The word crystallography comes from the Ancient Greek words κρύσταλλος (krústallos, meaning "clear ice, rock-crystal") and γράφειν (gráphein, meaning "to write"). This science helps us understand how tiny parts of materials are arranged, which tells us a lot about how those materials behave.

In July 2012, the United Nations recognized how important crystallography is by declaring 2014 the International Year of Crystallography. This shows just how useful this science is for the world.

Crystallography covers many areas, such as X-ray crystallography, which looks at how X-rays bounce off materials to show where atoms are located. It studies everything from the simple arrangements of atoms in crystals to more complex patterns, even those that are not periodic or form special structures called quasicrystals. This science is important in biology, chemistry, and physics, helping scientists discover new things in these fields.

History and timeline

Main articles: Timeline of crystallography and History of crystallography before X-rays

Long ago, scientists studied crystals by measuring the angles between their faces using tools like a goniometer. They plotted these measurements on special nets to understand the crystal's symmetry.

In the late 1800s, the discovery of X-rays and electrons changed everything. In 1912, Max von Laue conducted the first X-ray diffraction experiment, and in 1927, electrons were used in diffraction for the first time. These discoveries led to new ways to see inside crystals, creating the modern field of crystallography. Today, scientists use many tools, from small lab devices to huge facilities, to explore the tiny structures of crystals and make important discoveries.

Methodology

Main articles: X-ray crystallography, Electron diffraction, Neutron crystallography, and NMR crystallography

Crystallography studies how materials are arranged by looking at how beams of energy, like X-rays, bounce off them. These beams can also be electrons or neutrons, and each type gives different information about the material. For example, X-rays show where electrons are in the material, while electrons can be focused to create very detailed images. These methods help scientists understand the tiny building blocks of many things, from medicines to metals.

Applications in various areas

Crystallography helps scientists understand how atoms are arranged in materials. In materials science, it is used to study the shapes and properties of crystals. For example, the way iron changes its structure when heated can be examined using crystallography. This helps in creating new materials with specific properties.

In biology, crystallography is important for studying large molecules like proteins and DNA. Scientists use X-ray crystallography to see how these molecules are shaped. This knowledge helps in understanding how living things work at a tiny level. Structures of these molecules are stored in a database called the Protein Data Bank, which scientists can access freely.

Notation

Main article: Miller index

In crystallography, scientists use special symbols to describe directions and planes in crystals. For example, square brackets like [100] show a direction, while parentheses such as (100) describe a plane in the crystal. Angle brackets or chevrons group similar directions together due to symmetry, and curly brackets or braces group similar planes. These notations help scientists understand how crystals are built and how they behave.

Reference literature

The International Tables for Crystallography is a series of eight books that explain how scientists describe and study crystals. These books cover methods and math used to find out the structure of crystals using special tools like x-ray beams. Each book has about 1000 pages, and they focus on the steps and rules for studying crystals rather than listing the features of each crystal. The titles of the books include topics like crystal symmetry, math tables, and how crystals work.

Notable scientists

Crystallography has been advanced by many important scientists throughout history. Some of the notable figures in this field include William Henry Bragg, William Lawrence Bragg, Francis Crick, Rosalind Franklin, Dorothy Crowfoot Hodgkin, and Ada Yonath. These scientists, along with many others, have made significant contributions to our understanding of how atoms and molecules are arranged in crystals. Their work helps us learn about the structure of materials and living things at the molecular level.