Nitrogen in diamond

Evans T. (1992) Aggregation of nitrogen in diamond. In The Properties of Natural and Synthetic Diamond (ed. J. E. Field). Academic Press, London, pp. 259 -290. 

Besides the substitutional/interstitial location of the same FA, other centres can exist where more than one FA are involved, like the nn substitutional pairs for chalcogens in silicon or nitrogen in diamond so that in these cases, one must consider a universal value of solubility of the FAs. 

The classic example of precipitate nucleation in metals is the formation of GP zones in Al-Cu alloys. In ceramics, analogous examples include spinel in NiO, rutile in sapphire, or platelets of nitrogen in diamond. When particles are very small, the surface energy dominates. The calculation in Eqs. Box 15.1-Box 15.4 is instructive. Remember that the calculation is for a spherical nucleus and it ignores kinetics kinetics are actually important as we saw in Figure 15.5. 

The success of this approach evidences that the extension of the sp hybrid bonding of oxygen to carbon and nitrogen is on an essentially correct track. The sp hybrid bonding of nitrogen helps to understand why it is more difihcult to form the crystalline carbon nitride than the hexagonal SiCN crystallite [99] and that overdose (>75 % partial pressure) of nitrogen in diamond deposition could turn the diamond to SiCN [100]. 

Because Raman spectroscopy requires one only to guide a laser beam to the sample and extract a scattered beam, the technique is easily adaptable to measurements as a function of temperature and pressure. High temperatures can be achieved by using a small furnace built into the sample compartment. Low temperatures, easily to 78 K (liquid nitrogen) and with some diflSculty to 4.2 K (liquid helium), can be achieved with various commercially available cryostats. Chambers suitable for Raman spectroscopy to pressures of a few hundred MPa can be constructed using sapphire windows for the laser and scattered beams. However, Raman spectroscopy is the characterizadon tool of choice in diamond-anvil high-pressure cells, which produce pressures well in excess of 100 GPa. ... 

The Tetrahedral Carbon Atom.—We have thus derived the result that an atom in which only s and p eigenfunctions contribute to bond formation and in which the quantization in polar coordinates is broken can form one, two, three, or four equivalent bonds, which are directed toward the corners of a regular tetrahedron (Fig. 4). This calculation provides the quantum mechanical justification of the chemist s tetrahedral carbon atom, present in diamond and all aliphatic carbon compounds, and for the tetrahedral quadrivalent nitrogen atom, the tetrahedral phosphorus atom, as in phosphonium compounds, the tetrahedral boron atom in B2H6 (involving single-electron bonds), and many other such atoms. 

The diffraction pattern obtained in the detector plane when the beam scan in a STEM instrument is stopped at a chosen point of the image comes from the illuminated area of the specimen which may be as small as 3X in diameter. In order to form a probe of this diameter it is necessary to illuminate the specimen with a convergent beam. The pattern obtained is then a convergent beam electron diffraction (CBED) pattern in which the central spot and all diffraction spots from a thin crystal are large discs rather than sharp maxima. Such patterns can normally be interpreted only by comparison with patterns calculated for particular postulated distributions of atoms. This has been attempted, as yet, for only a few cases such as on the diffraction study of the planar, nitrogen-rich defects in diamonds (21). 

The color of diamond due to nitrogen impurities has been described in Section 9.6.3 It has been found that nitrogen impurities that are located next to a carbon vacancy in diamond thin films endow the solid with quite new properties, somewhat similar to the properties of a solid containing FLi centers compared with ordinary F centers. The diamond structure is built up of carbon atoms each surrounded by four... 

Figure 9.27 A (N-V) center in diamond, consisting of a carbon atom vacancy and a neighboring nitrogen atom impurity.

W. Qiu, Y.K. Vohra and S.T. Weir, Role of nitrogen in the homoepitaxial growth on diamond anvils by microwave plasma chemical vapor deposition, J. Mater. Res., 22, 1112-1117 (2007). 

Kirkley MB, Gurney JJ, Otter ML, HiU SJ, Daniels LR (1991) The application of C-isotope measurements to the identification of the sources of C in diamonds. Appl Geochem 6 477 94 Kirshenbaum I, Smith JS, Crowell T, Graff J, McKee R (1947) Separation of the nitrogen isotopes by the exchange reaction between ammonia and solutions of ammonium nitrate. J Chem Phys 15 44(M46... 

The luminescence of diamonds is related to various defects in its structure. Almost always, luminescence centers in diamonds are related to N atoms. It is logical, because the atomic radii of C and N are nearly equal (approximately 0.77 A). Luminescence spectroscopy has proven to be the most widely used method in studies of diamonds even in comparison with optical absorption, ESR, IR and Raman spectroscopies. Himdreds of spectra have been obtained, fluorescence characteristics enter into diamond quality gemological certificates, a wide range of electronic and laser applications are based on diamond optical properties in excited states nitrogen center aggregation is controlled by the residence time of diamond in the mantle, distinction between natural... 

Demirplak and Rice developed the counter-diabatic control protocol while studying control methods that efficiently transfer population between a selected initial state and a selected target state of an isolated molecule [11-13]. The protocol has been studied for manipulation of atomic and molecular states [11, 12, 19] and spin chain systems [20, 21]. Experiments with the counter-diabatic protocol have been demonstrated for the control of BECs [22] and the electron spin of a single nitrogen-vacancy center in diamond [23]. The counter-diabatic field (CDF) protocol is identical with the transitionless driving protocol, independently proposed by Berry a few years later [24]. A discussion of the relationship between these approaches and several of the other proposed shortcuts to adiabaticity can be found in the review by Torrontegui and coworkers [10]. 

Effect of pH on the yield of formaldehyde (triangle) and nitrogen dioxide (diamond) produced from peroxynitrous acid attack upon 100 mM DMSO. All reactions were conducted at 37°C in 50 mM potassium phosphate buffer. The pH was measured after the addition of peroxynitrite to account for the alkaline peroxynitrite addition. Peroxynitrite did not attack 24 /iM formaldehyde (circle) under the reactions conditions utilized. 

Figure 1. Nitrogen abundance in diamonds from various meteorite types.

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