Diamonds physical properties

R. Berman, ed.. Physical Properties of Diamond, Clarendon Press, Oxford, 1965. 

R. M. Chrenko and H. M. Strong, Physical Properties of Diamond, General Electric Research and Development Report No. 75CRD089, Oct. 1975, pp. 

Some physical properties of the elements are compared in Table 10,2. Germanium forms brittle, grey-white lustrous crystals with the diamond structure it is a metalloid with a similar electrical resistivity to Si at room temperature but with a substantially smaller band gap. Its mp, bp and associated enthalpy changes are also lower than for Si and this trend continues for Sn and Pb which are both very soft, low-melting metals. 

Compare the hybridization and structure of carbon in diamond and graphite. How do these features explain the physical properties of the two allotropes ... 

Ionic bonds may be fully as strong as covalent bonds, so that properties such as hardness, solubility, melting point, ionization in solution, and chemical character are not especially valuable criteria as a rule. Sometimes comparison of properties with those of compounds of known bond type permits reasonably certain conclusions to be drawn. Thus the similarity in physical properties as well as in atomic arrangement of SiC, AIN, and diamond suggests that all three substances contain covalent bonds. PbS is like FeS2, MoS2, etc. in properties rather than like CaS, so that it is improbable that PbS is an ionic substance. 

Structural chemistry is an essential part of modern chemistry in theory and practice. To understand the processes taking place during a chemical reaction and to render it possible to design experiments for the synthesis of new compounds, a knowledge of the structures of the compounds involved is essential. Chemical and physical properties of a substance can only be understood when its structure is known. The enormous influence that the structure of a material has on its properties can be seen by the comparison of graphite and diamond both consist only of carbon, and yet they differ widely in their physical and chemical properties. 

A number of chemical elements, mainly oxygen and carbon but also others, such as tin, phosphorus, and sulfur, occur naturally in more than one form. The various forms differ from one another in their physical properties and also, less frequently, in some of their chemical properties. The characteristic of some elements to exist in two or more modifications is known as allotropy, and the different modifications of each element are known as its allotropes. The phenomenon of allotropy is generally attributed to dissimilarities in the way the component atoms bond to each other in each allotrope either variation in the number of atoms bonded to form a molecule, as in the allotropes oxygen and ozone, or to differences in the crystal structure of solids such as graphite and diamond, the allotropes of carbon. 

The packing arrangement of atoms or molecules in a crystalline solid phase is generally not unique, and for organic molecules in particular, it is common for two or more crystalline forms of the same substance to exist. The most familiar example in elemental terms is Graphite and Diamond. Both are composed entirely of the element Carbon, however their ciystal structures are very different, and so too are their physical properties. Calcium Carbonate is another common example with three polymorphic forms Calcite, Aragonite and Vaterite. 

There are four allotropic forms of manganese, which means each of its allotropes has a different crystal form and molecular structure. Therefore, each allotrope exhibits different chemical and physical properties (see the forms of carbon—diamond, carbon black, and graphite). The alpha (a) allotrope is stable at room temperature whereas the gamma (y) form is soft, bendable, and easy to cut. The delta A allotrope exists only at temperatures above 1,100°C. As a pure metal, it cannot be worked into different shapes because it is too brittle. Manganese is responsible for the color in amethyst crystals and is used to make amethyst-colored glass. 

Diamond luminescence was studied mainly with the two following aims to carry out a fundamental investigation of its physical properties and to determine the optimal conditions for luminescent sorting of diamond bearing rocks. For the first task, diamond photoluminescence was studied at liquid nitrogen temperature at which luminescence centers are marked by characteristic zero-phonon fines and are much more informative then at room temperature. For the second task, were diamond is one of the first minerals for which luminescence sorting was used, liuninescence properties should be studied at 300 K. In the first stages it was established that X-ray luminescence of the A-band... 

In addition to C onions, C atoms condense into various kinds of chemically bonded forms, and they are known to have excellent physical properties depending on the bonding nature. This means that research and applications not only in the materials science but also in other scientific fields are expected. At JAERI, the optimum growth conditions have been successfully obtained for the preparation of high-quality Cgo, diamondlike carbon, and nanocrystalline diamond by means of ion-beam-assisted deposition [80-82]. The susceptibility of Ni/Cgo thin films to thermal treatment, the formation of nanocrystalline diamond and nanotubes due to codeposition of Co and Ceo, and the surface modification of glassy... 

In diamond C, it is the fact that the structure consists of sp covalent bonds only that accounts for its unique physical properties, such as the highest hardness of any material (Mohs hardness 10), small compressibility (1.7X10 cm /l ), the highest elasticity among any known material (4 6 X10 dynes/cm, bulk elasticity), large thermal conductivity (9 26 W/(deg cm)), and small thermal expansion coefficient (0.8 0.1 X10 at 20 °C, comparable to the value of invar). As a result. 

F. C. Frank and A. R. Lang, X-ray topography of diamond, in Physical Properties of Diamond, ed. R. Berman, Oxford, Clarendon Press, 1965, pp. 69-115... 

The different allotropes of carbon have very different physical properties. Graphite (used as pencil lead) is black and soft, while diamonds are clear and very hard. On a scale of 1 to 10, graphite has a hardness of between 1 and 2, while diamonds have a hardness of 10. 

We shall now discuss the method of crystal growth and the electronic properties of GaAs, a typical example of a III-V compound which is expected to become more useful than Si and Ge in the near future, concentrating on the relation between non-stoichiometry and physical properties. GaAs has a zinc blende type structure, which can be regarded as an interpenetration of two structures with face centred cubic lattices, as shown in Fig. 3.29. Disregarding the atomic species, the structure is the same as a diamond-type... 

The necessary atomic mobility can be provided by heating to about 1500 K (area D in Fig. 1). Various departures from ideality make it difficult to prepare pure wurtzitic carbon, even when the best graphite is used. The products obtained so far always contain some ordinary diamond as well as remnant graphite, parts of which are compressed by the nearby diamond regions. Hence, many physical properties of wurtzitic carbon are not well-known. It has been found in the Canyon Diablo meteorite and in some shock-made diamond from DuPont, but not in regular synthetic industrial diamond. This form of carbon has been given the name lonsdaleite. 

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