X-ray Diffraction Laboratory


The crystal structure is defined as the three-dimensional arrangement of atoms in a crystalline solid.  If the atoms constitute a molecule than that arrangement is known as a molecular structure.  On the other hand, if the atoms form a solid, such as sodium chloride, the solid is called an extended structure or solid-state structure.   We employ X-ray Diffraction to determine structure (see FAQ).  The crystal structure example shown is for tetraazacyclododecane.  The X-ray crystal structure determination will locate the average position of the electrons in the crystal, which in turn determines the position of the atoms.  If we trace the paths of the electrons, we will trace a rough sphere in space, which can be represented by a ball.  Electrons are also located between atoms and constitute the chemical bond, which we represent with sticks.  The resulting molecular structure plot is known as a stick and ball model and is shown below. cyclen

 One of the truly unique characteristics of an X-ray crystal structure is the ability to view the structure in three-dimensions.  To illustrate this the tetraazadodecane structure is spun 360 deg.pack

Employing the crystal's property of order and symmetry we can build a mini-crystal from the molecular structures positions.  The mini-crystal represents what the bulk crystal would look like if we could view objects directly at the atomic level in three dimensions. (If It was possible to view atoms with a light microscope)