Chalcopyrite crystal structures

For noncubic compounds, the bulk crystal may be optically anisotropic. This is the case not only for wurtzite or chalcopyrite crystal structures but also for ternary and quaternary III-V and II-VI compounds showing ordering effects on the sublattices. In aU these cases, the compound semiconductor is an optically anisotropic material. The RAS signal is then a superposition of two contributions, one originating from the bulk and the other from the surface. In order to analyze the surface, the two contributions have to be separated, a task for optical modeling. 

The most controversial and contradicting problem is, perhaps, the natural and collectorless floatability of sulphide minerals. Gaudin (1957) classified the natural hydrophobicity of different minerals according to their crystal structure and showed that most sulphide minerals were naturally hydrophobic to some extent, which had been fiirther proved based on van der Waals theory by Chander (1988, 1999). Lepetic (1974) revealed the natural floatability of chalcopyrite in dry grinding. Finklestein (1975, 1977) demonstrated that orpiment, realgar and molybdenite were naturally floatable, and that pyrite and chalcopyrite had natural floatability at certain conditions due to the formation of surface elemental sulphur. Buckley and Woods (1990,1996) attributed the natural floatability of chalcopyrite... 

The copper, copper-iron, and the silver sulfides are more complex than the sulfides discussed previously, containing several cations or cation sites in their structures. Thus chalcopyrite (CuFeSj), although having a fairly simple structure based on that of sphalerite, but with Cu and Fe alternately replacing Zn atoms, contains both Cu+ and Fe + in regular tetrahedral coordination (as indicated by neutron diffraction and Moss-bauer studies see Vaughan and Craig, 1978). A family of more than thirty synthetic compounds with the chalcopyrite structure is known, and their properties have been studied because of potential applications as semiconductors. Miller et al. (1981) have reviewed the crystal structures, vibrational properties, and band structures of these materials. 

The kesterite structure Cu2ZnSnS4 is isoelectronic with chalcopyrite CulnS2. Half of the In(III) atoms are replaced with Zn(II) atoms, and the other half are replaced with Sn(lV) atoms. The crystal structures of the chalcopyrite and kesterite are shown in Figure 1.3. 

The diversity in structure and bonding possible for phosphides is effectively demonstrated by the monophosphides. Monophosphides MP of the group 1 and 2 elements (El, E2) are polyphosphides with i(P ) chains and P2" dumbbells, respectively. Ell and E12 monophosphides are not known. The E3 and E13 monophosphides are the so-called normal compounds with 3x = (M) (see Section 2). With El3, they form the zinc blende structure with tetrahedral heteroatomic bonds. Ternary derivatives such as MgGeP2 and CuSi2P3 have a random distribution of the M atoms, whereas CdGeP2, crystallizes in the ordered chalcopyrite type with a TO[GeP4/2] tetrahedral net (see Section 6.4). The E3 monophosphides form the NaCl structure. CeP is remarkable because of its physical properties (metal-semiconductor transition heavy-fermion behavior). The E14 monophosphides show the break usually observed when passing the Zintl border. Binary lead phosphides are not known SiP and GeP... 

X-Ray diffraction studies show that all members of the CuGa xFexS2 series (O x l.O) crystallize with the chalcopyrite structure.549 When x = 0.025 the magnetic moment for Fe approaches the spin-only value (5.92 B.M.). 

The preparation and characterization of the two phases Caio- Si,2-2 As,(, and Caio, Si]2- Pi6 (0.66 X 2.50) have been described.Their structures are isotypic and crystallize with monoclinic symmetry, of space group they may be related to a slightly distorted NaCl-type. Their unit-cell parameters are included in Table 27. A comparison of the different methods of crystal growth of ZnSiP2, ZnSiAs2, and CdGeAs2 (chalcopyrite structures) has also been undertaken. " ... 

The most prevalent ternary chalcopyrite materials are jo-type Cu(In Ga)(S Se)2 (CIGS), which crystallize in the tetragonal chalcopyrite structure and are used in the photovoltaic modules. The complexity of the phase diagrams for Cu-III-VI materials results in a large number of intrinsic... 

The zonal structure is remarkably conserved between the modern hydrothermal vent systems and the ancient volcanogenic massive sulfide (VMS) deposits of hydrothermal origin. VMS deposits can reach many kilometres in diameter, and date back to the Archean period [185-187]. The ancient VMS deposits have pyrite (FeS2) and chalcopyrite (CuFeS2) at their centres being encircled by consecutive halos of, e.g., pyrite-chalcopyrite-sphalerite, sphalerite-galena-alabandite, and, finally, chert [185,187]. ZnS crystals Unique traits... 

AiiBi cy and A B CY compounds (chalcopyrites) are chemically and structurally close analogues of A B and A B compounds. Because of the difference between the A-C and B-C distances the tetrahedra are slightly distorted and, if the A and B atoms form ordered sublattices, the crystals are tetragonal rather than cubic. In some compounds, e.g. in... 

The ternary semiconductors of the type CuInSe, AglnSe, etc. crystallize in the chalcopyrite structure whose unxt cell is compared to that of the zincblend structure in Fig. 18. 

If we neglect the H atom in LiOH then its structure corresponds to the anti-PbO type. Since the axial ratio and the free positional parameter of this tetragonal structure can vary in a certain range, different isopuntal structure [9] types are possible. Thus for c/a = V2 and z(anion) = j, a cubic close-packing of the anions results with the cations in tetrahedral holes. An axial ratio c/a = 1/V2 and an anion parameter z =, on the other hand, correspond to the CsCl type with coordination number 8. As follows from Table 56, LiOH approximates a cubic close-packing with Li in deformed tetrahedral coordination. The position of the lone electron pair of PbO is here taken by H (corrected O—H distance 0.98 A [325] similar to the lone pair-cation distance). The electron density corresponds to Li 0 ° H and one electron smeared between the layers [1012]. In Table 55, LiOH is compared with chemically related compounds. Lithium amide has a closely related structure in which the layers of tetrahedral cation sites are alternately I and i occupied (5T1 + IT2 and ti, respectively) instead of the completely occupied and completely empty layers of LiOH. This is obviously a consequence of the weaker dipole character of NHJ. LiF, with no dipole moment, crystallizes in the rocksalt structure. The structure of LiSH is similar to chalcopyrite whereas that of the hydrosulfides and hydroselenides of Na, K and Rb is a rhombohedrally deformed rocksalt type. 

There are practical problems in achieving a true virtual crystal. For example, to avoid some amount of disorder in the lattice, the average number of A atoms which were second-nearest-neighbors to B atoms in an Ai.xBxC alloy would have to be constant. At a composition of x = 0.5, this would mean that every B atom would have two A atoms and two B atoms for second-nearest-neighbors. This arrangement exists in some materials and leads to structures such as chalcopyrite. Such a well-organized structure is no longer a random alloy. Rather, it is a new compound with unique symmetry and, consequently, a different band structure. Thus, even in the perfectly distributed alloy case, one can expect to have deviations from a virtual crystal behavior because a perfect distribution is not random. The reason a virtual crystal... 

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