Crystalline solids have sharp and very high melting points, indicating the presence of a long range order arrangement in them.

Their mechanical, electrical and optical properties do not depend upon the direction along which they are measured. They are isotropic and in this respect resemble liquids and are sometimes referred to as super-cooled liquids.

The space group (or crystallographic group, or fedorov group) of a crystal is a description of the symmetry of the crystal, and can be one of 230 types.

These are bad conductors of electricity and are regarded as electrical insulators.

In the hexagonal system, we have an additional axes which gives the crystals six sides. Three of these are equal in length and meet at 60° to each other. The C or vertical axis is at 90° to the shorter axes. Mineralogists sometimes divide this into two systems, the hexagonal and the trigonal, based on their external appearance.

Most solids become liquids when heated. Some undergo sublimation on heating. The temperature at which a solid changes into liquid is called the melting point and the process is called as melting. Due to the varying natures of solids their melting temperatures vary considerably.

Point defects are defects that occur only at or around a single lattice point. They are not extended in space in any dimension. Strict limits for how small a point defect is, are generally not defined explicitly, but typically these defects involve at most a few extra or missing atoms.

The trigonal crystal system is one of the seven crystal systems. It consists of the five point groups of the seven space groups with a rhombohedral lattice. In the classification into 6 crystal families, the trigonal crystal system is combined with the hexagonal crystal system and grouped into a larger hexagonal family.

Deep Level Transient Spectroscopy (DLTS) is an experimental tool for studying electrically active defects in semiconductors. DLTS investigates defects present in a space charge (depletion) region of a simple electronic device. The most commonly used are Schottky diodes or p-n junctions.

A grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material.

Recrystallization is a process by which deformed grains are replaced by a new set of undeformed grains that nucleate and grow until the original grains have been entirely consumed. Recrystallization is usually accompanied by a reduction in the strength and hardness of a material and a simultaneous increase in the ductility.

The presence of dislocations strongly influences many of the properties of materials. This theory was originally developed by Vito Volterra in 1905, but the term 'dislocation' was coined later by the late Professor Sir Frederick Charles Frank of the Physics Department at the University of Bristol.

Silicon carbide (SiC), also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. SiC is widely used in high-temperature/high-voltage semiconductor electronics.

A schottky defect is a type of point defect in a crystal lattice. This defect occurs when oppositely charged ions leave their lattice sites while creating vacancies. These vacancies are formed in stoichiometric units to maintain an overall neutral charge in the ionic solid. The vacancies are then free to move about as their own entities. Normally these defects lead to a decrease in the density of the crystal.

They are poor conductors of electricity and therefore, are insulators in the solid state.

In molecular crystals, the constituent particles are molecules. These molecules are held together by weak forces known as Van der Waal's forces. Common examples are dry ice, wax, iodine, sulphur, etc.

Paramagnetic materials have a small, positive susceptibility to magnetic fields. These materials are slightly attracted by a magnetic field and the material does not retain the magnetic properties when the external field is removed. Paramagnetic properties are due to the presence of some unpaired electrons.

Substances whose constituents are not arranged in an orderly manner are called amorphous solids. They are also called pseudo-solids, and differ from crystalline solids in many respects. The common examples of amorphous solids are -  glass, rubber, fused silica, plastics, etc.

Zinc, also referred to in non-scientific contexts as spelter, is a bluish-white, lustrous, diamagnetic metal though most common commercial grades of the metal have a dull finish. It is somewhat less dense than iron and has a hexagonal crystal structure.

Iron is a metal in the first transition series. It is the most common element in the whole planet Earth, forming much of the earth's outer and inner core, and it is the fourth most common element in the earth's crust. It is ferromagnetic around room temperature.

Crystal habit is an overall description of the visible external shape of a mineral. This description can apply to an individual crystal or an assembly of crystals or aggregates.

In crystallography, the space group of a crystal is a description of the symmetry of the crystal and can have one of 230 types.

A bjerrum defect is a crystallographic defect which is specific to ice, and which is partly responsible for the electrical properties of ice. A hydrogen bond normally has one proton, but a hydrogen bond with a bjerrum defect will have either two protons (D defect) or no proton (L defect). The unfavorable defect strain is resolved when a water molecule pivots about an oxygen atom to produce hydrogen bonds with single protons.

Crystallography is the experimental science of the arrangement of atoms in solids. The word crystallography derives from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and grapho = write.

They are extremely non-volatile and have very high melting points.