File Name: difference between crystalline and amorphous solids .zip
Polymers are unlike other types of materials because of their high molecular weight. Molecular weight is the value used to express the size of a molecule. Water, for example, has a molecular weight of 18 atomic mass units. Polymers are much larger, with molecular weights ranging from tens of thousands up to several million atomic mass units. The sheer size of polymers has a great impact on their unique properties. One important implication of polymer size is how atoms behave in different phase states.
Amorphous forms are, by definition, non-crystalline materials which possess no long-range order. The amorphous solids have always been an essential part of pharmaceutical research, but the current interest has been raised by two developments: a growing attention to pharmaceutical solids in general, especially polymorphs and solvates and a revived interest in the science of glasses and the glass transition. Amorphous substances may be formed both intentionally and unintentionally during normal pharmaceutical manufactoring operations. The properties of amorphous materials can be exploited to improve the performance of pharmaceutical dosage forms, but these properties can also give rise to unwanted effects that need to be understood and managed in order for the systems to perform as required. The degree of crystallinity, according to the USP, depends on the fraction of crystalline material in the mixture, which is termed the two-state model. Another way of viewing this situation is that the crystallinity has a range from percent for perfect crystals zero entropy to 0 percent non-crystalline or amorphous ; this is known as the onestate model 2. Amorphous solids exist in many industrially important products, such as polymers, ceramics, metals, optical materials glasses and fibers , foods, and pharmaceuticals.
12.1: Crystalline and Amorphous Solids
Surface Science pp Cite as. The atomic structure of crystalline silicon surfaces and amorphous silicon films deviates markedly from the tetrahedral symmetry found in the bulk diamond lattice structure. Consequently, strained bonds, distorted bond angles and unsaturated bonds are present which lead to characteristic features in the electronic density of states and relate to specific interactions with hydrogen. Similar properties found for the two systems are outlined. Correlated research may help to answer still existing open questions. Unable to display preview.
possess a definite and regular geometry and consist of both long-range as well as short-range order of its constituent particles. The particles of the constituents.
Amorphous vs. Crystalline Polymers
As you should remember from the kinetic molecular theory, the molecules in solids are not moving in the same manner as those in liquids or gases. Solid molecules simply vibrate and rotate in place rather than move about. Solids are generally held together by ionic or strong covalent bonding, and the attractive forces between the atoms, ions, or molecules in solids are very strong. In fact, these forces are so strong that particles in a solid are held in fixed positions and have very little freedom of movement. Solids have definite shapes and definite volumes and are not compressible to any extent.
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Amorphous solid , any noncrystalline solid in which the atoms and molecules are not organized in a definite lattice pattern. Such solids include glass, plastic , and gel. Solids and liquids are both forms of condensed matter; both are composed of atoms in close proximity to each other. But their properties are, of course, enormously different.
A crystal or crystalline solid is a solid material whose constituents such as atoms , molecules , or ions are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification. Examples of large crystals include snowflakes , diamonds , and table salt. Most inorganic solids are not crystals but polycrystals , i.