Source: Laboratory of Dr. Jimmy Franco - Merrimack College

X-ray crystallography is a method commonly used to determine the spatial arrangement of atoms in a crystalline solid, which allows for the determination of the three-dimensional shape of a molecule or complex. Determining the three-dimensional structure of a compound is of particular importance, since a compound's structure and function are intimately related. Information about a compound's structure is often used to explain its behavior or reactivity. This is one of the most useful techniques for solving the three-dimensional structure of a compound or complex, and in some cases it may be the only viable method for determining the structure. Growing X-ray quality crystals is the key component of X-ray crystallography. The size and quality of the crystal is often highly dependent on the composition of the compound being examined by X-ray crystallography. Typically compounds containing heavier atoms produce a greater diffraction pattern, thus require smaller crystals. Generally, single crystals with well-defined faces are optimal, and typically for organic compounds, the crystals need to be larger than those containing heavy atoms. Without viable crystals, X-ray crystallography is not feasible. Some molecules are inherently more crystalline than others, thus the difficulty of obtaining X-ray quality crystals can vary between compounds. The growth of X-ray crystals is similar to the process of recrystallization that is commonly used for purifying compounds, but with an emphasis on producing higher quality crystals. Often, higher quality crystals can be obtained by allowing the crystallization process to proceed slowly, which may occur over the course of day or months.