Can you rephrase this? It's not making any sense to me in terms of stoichiometry. Are you talking about lattice defects when you say "sites?"tirrel said:after an Xray analysys I find that in a material a site can be occupied by an atom of type 1 or an atom of type 2 with 50 % probability
Non-stoichiometry refers to the deviation of a chemical compound from its ideal or expected elemental composition. This can occur due to a variety of reasons, such as the presence of impurities, defects, or the formation of solid solutions.
Partial occupancies are a result of non-stoichiometry in a crystal structure. This means that some of the atomic positions within the crystal are not fully occupied by a single type of atom, but rather have a mixture of two or more types of atoms occupying the same position.
Partial occupancies are usually represented by using fractional coordinates in crystal structure diagrams, where the fraction represents the proportion of the atom occupying that particular position. For example, a fractional coordinate of 0.5 means that the atom is occupying half of the position.
The presence of partial occupancies can significantly affect the physical and chemical properties of a crystal. This is because the different types of atoms occupying the same position can lead to changes in the crystal's structure, bonding, and overall stability.
Scientists use various analytical techniques such as X-ray diffraction, spectroscopy, and electron microscopy to study non-stoichiometry and partial occupancies in crystals. These techniques can provide information about the composition, structure, and properties of the crystal, allowing for a better understanding of these phenomena.