Cubic closest packing system

Fig. 4.14 Unit cells in the cubic closest packed systems, (a) A face-ccntcred array of atoms. Note that the exposed layer consists of a closest packed array of fifteen atoms. Consider this the A layer , (b) A closest packed layer of six atoms placed on (a). Consider this the B layer, (c) The final atom, a member of the C layer, is added to complete the cube. The fee unit cell is redrawn in (d. Note that the single atom that composes the C layer does net lie above any atom in the A layer (as it would if ths were hep).

One could follow a similar practice and construct a similar hexagonal sandwich with two layers (B, Q of filler, but a cubic cell of higher symmetry can be. constructed the second system is thus characterized as cubic closest packed. The relation between the cubic unit cell (which is identical to the face-centered cubic cell we <... 

Crystal systems, 75 Cubic closest packed (ccp) system. 120... 

Molecular dynamics calculations of Hoover and Ree (25) have indicated that a fluid-solid transition occurs in a system of hard spheres even in the absence of attractive forces. The fluid exists for particle volume fractions up to a value rj = 0.49 and at this point, a solid phase with ij = 0.55 is predicted to coexist in equilibrium with the fluid phase. When the particle volume fraction lies in the range 0.55 < jj < 0.74, the solid phase is stable. The upper limit for ij corresponds to the density at closest packing for a face-centered-cubic (fee) arrangement of the particles. 

Slip occurs along specific crystal planes (slip planes) and in specific directions (slip directions) within a crystal structure. Slip planes are usually the closest-packed planes, and slip directions are the closest-packed directions. Both face-centered-cubic (FCC) and hexagonal-close packed (HCP) structure are close packed structures, and slip always occurs in a close packed direction on a closepacked plane. The body-centered-cubic (BCC) structure is not, however, close packed. In a BCC system, slip may occur on several nearly close packed planes or directions. Slip planes and directions, as well as the number of independent slip systems (the product of the numbers of independent planes and directions), for these three structures are listed in Table 7.2. 

The body-centred cubic crystal is not close-packed. The slip systems with the closest packed directions and planes in this lattice are of the type 110 (111) (figure 6.15). With two slip directions per plane and six different slip planes, twelve slip systems result. As summarised in table 6.2, slip is also possible on other crystallographic planes that are only slightly more difficult to activate [55]. 

The three types of unit cells of the cubic system are simple, body-centered, and face-centered. The highest packing efficiency occurs with cubic (face-centered) and hexagonal closest packing. 

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