<P> With the continuing advances being made in the production of synthetic diamond, future applications are beginning to become feasible . Garnering much excitement is the possible use of diamond as a semiconductor suitable to build microchips from, or the use of diamond as a heat sink in electronics . Significant research efforts in Japan, Europe, and the United States are under way to capitalize on the potential offered by diamond's unique material properties, combined with increased quality and quantity of supply starting to become available from synthetic diamond manufacturers . </P> <P> Each carbon atom in a diamond is covalently bonded to four other carbons in a tetrahedron . These tetrahedrons together form a 3 - dimensional network of six - membered carbon rings (similar to cyclohexane), in the chair conformation, allowing for zero bond angle strain . This stable network of covalent bonds and hexagonal rings, is the reason that diamond is so strong . Although graphite is the most stable allotrope of carbon under standard laboratory conditions (273 or 298 K, 1 atm), a recent computational study indicated that under idealized conditions (T = 0, p = 0), diamond is the most stable allotrope by 1.1 kJ / mol compared to graphite . </P> <P> Graphite, named by Abraham Gottlob Werner in 1789, from the Greek γράφειν (graphein, "to draw / write", for its use in pencils) is one of the most common allotropes of carbon . Unlike diamond, graphite is an electrical conductor . Thus, it can be used in, for instance, electrical arc lamp electrodes . Likewise, under standard conditions, graphite is the most stable form of carbon . Therefore, it is used in thermochemistry as the standard state for defining the heat of formation of carbon compounds . </P> <P> Graphite conducts electricity, due to delocalization of the pi bond electrons above and below the planes of the carbon atoms . These electrons are free to move, so are able to conduct electricity . However, the electricity is only conducted along the plane of the layers . In diamond, all four outer electrons of each carbon atom are' localised' between the atoms in covalent bonding . The movement of electrons is restricted and diamond does not conduct an electric current . In graphite, each carbon atom uses only 3 of its 4 outer energy level electrons in covalently bonding to three other carbon atoms in a plane . Each carbon atom contributes one electron to a delocalised system of electrons that is also a part of the chemical bonding . The delocalised electrons are free to move throughout the plane . For this reason, graphite conducts electricity along the planes of carbon atoms, but does not conduct in a direction at right angles to the plane . </P>

Which of the allotrope of carbon is a constituent of a lead pencil