Amorphous and Crystalline Solids

Introduction

Crystalline solids and amorphous solids are two types of solids formed from atoms, ions or molecules. Molecular, ionic, covalent and metallic crystalline solids are the main types of crystals formed from constituents with defined structures. An amorphous solid is a material without a well-defined structure and precise melting point. Both amorphous and crystalline have distinct characters. In chemistry, solid molecules are characterised by their final shape, strength, density and stiffness, not by liquids and gases. Solids are rigid due to the lack of translational motion of structural elements. The units are held in their middle with a strong attraction.

Crystalline Solid

Crystalline solids or crystals have characteristic internal structures, which in turn result in characteristic planes or planes. These planes intersect at a material-specific angle. When disclosed to X-rays, a unique pattern is demonstrated by each structure that can be utilised to identify the material. The size of the crystal does not depend on the features or aspects of the angles; they reflect the cosistantely frequent configuration in space of the constituents of atoms, molecules or ions. For example, when an ionic crystal is cut, repulsive interactions cause it to fracture along the solid plane, creating new planes that are at the same angle as the original crystal. In covalent solids like cut diamonds, the angle at which the planes meet is also not random, but rather is determined by the arrangement of carbon atoms in the crystal.

Uses of Crystalline Solids

The metals and ceramics, which we use in our daily life, are actually crystalline. For example, steel, copper alloy, aluminium alloy, etc. are all crystalline metal materials. Under certain processing conditions, such as the very rapid cooling of the metal, the metal can become amorphous. They are called metallic glasses. Similarly, ceramics such as Al2O3 and SiC are crystalline but can be transformed into an amorphous phase. A typical example is SiO2, whose crystalline (e.g. quartz) and amorphous (e.g. fused silica) phases are common.

Amorphous Solids

Generally, amorphous solids have two characteristics. When cut or cracked, they generate fragments of irregular, usually curved surfaces; and they have ill-defined arrangements when disclosed to X-rays because their components are not systematically arranged in a regular grid. Amorphous, translucent solids are called glass. If the liquid phase is cooled fast enough, then most of the substance can solidify into an amorphous form. However, some solids are amorphous in nature because their compositions are not matched enough to form a steady lattice, or because they contain impurities that derange the lattice. For example, while quartz crystal and quartz glass share the same chemical composition and basic building blocks—both are SiO2, and both consist of bonded SiO4 tetrahedra—the arrangement of atoms in space differs. Crystalline quartz consists of highly ordered arrangements of silicon and oxygen atoms, the atoms are arranged almost randomly in quartz glasses. Quartz glass forms when molten SiO2 cools rapidly (4K/min), and the large ideal or flawless quartz crystals sold in mineral stores have cooled for thousands of years. In contrast, aluminium crystallises much faster. Amorphous aluminium forms exclusively when the liquid cools at an astonishing rate of 4 × 1013 K/s, preventing atoms from organising into regular networks.

Uses of Amorphous Solids

Some examples are Rubber, Glass, Plastic, Silica, etc.

Glass is widely used in food cans, soda bottles and other packaging, glassware, kitchen utensils and other tableware production and construction. Rubber is used to make leather bags, shoes, ropes, and as a raw material for other industrial materials. Plastics are widely used in the preparation of man-made fibres, Tupperware, bakelite boards, nylon ropes, etc. 

Silica is considered the photovoltaic material used in solar panels to convert solar energy into electricity.

Difference Between Amorphous and Crystalline Solids

Some are the substantial differences between crystalline and amorphous solids are given below :-

Crystalline solids have a clear structure and sharp melting point, but amorphous solids do not have a clear structure and sharp melting point.

The constituents of crystalline solids are widely ordered in a crystal lattice. But in an amorphous solid, the ingredients have no order.

Crystalline solids have definite heat of fusion, whereas amorphous solids have indefinite heat of fusion.

Anisotropy for crystalline solids is anisotropic, and for amorphous, it is isotropic.

Nature of crystalline is true solids, whereas amorphous have pseudo solids.

Conclusion

Solids are characterised by fine three-dimensional arrangements of atoms, ions, or molecules, whose components are often locked in their positions. The components can be arranged into a regularly repeating three-dimensional lattice (lattice), resulting in crystalline solids, or more or less arbitrarily, amorphous solids. Crystalline solids have well-defined edges and faces, bend X-rays and tend to have sharp melting points. Amorphous solids are in curved surfaces or have irregularity and do not show well-resolved X-ray diffraction patterns, and melt over the temperature of a wide range of spectrum. Crystalline solids have regularly ordered lattices held together by uniform intermolecular forces, whereas the components of amorphous solids are not arranged in a regular lattice.