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An Introduction to Metals
Published in Bankim Chandra Ray, Rajesh Kumar Prusty, Deepak Nayak, Phase Transformations and Heat Treatments of Steels, 2020
Bankim Chandra Ray, Rajesh Kumar Prusty, Deepak Nayak
As can be seen, the corner atoms are not touching each other. The face center atom of this right-side face (shown as atom “X”) touches the four corner atoms on that particular face, four face center atoms (top, bottom, front, and back) of the shown unit cell, and similarly four face center atoms of the adjacent right unit cell. Thus, an atom is having 12 nearest neighboring atoms, and therefore, the coordination number of an FCC atom is 12. A representative of the atomic location in the unit cell is shown in Figure 1.5c. However, note that in this figure the spheres (corner and face center) represent the center of the atom (readers should not assume the size of this sphere to be the same as that of the corresponding atom; it is just for the sake of simple representation).
Crystal Chemistry and Specific Crystal Structures
Published in David W. Richerson, William E. Lee, Modern Ceramic Engineering, 2018
David W. Richerson, William E. Lee
The FCC structure is common among metals (copper, nickel, aluminum, lead, silver). As shown in Figure 5.6,5 it consists of atoms at each corner of a cube and at the center of each cube face. Each unit cell contains four atoms. Each atom is surrounded by 12 identical atoms and thus has a CN of 12. A CN of 12 is the tightest packing possible for atoms all of a single size and results in a close-packed structure with a packing factor (PF) of 0.74. The PF is determined by using the hard-ball model of a unit cell in Figure 5.6a. The PF equals the volume of the balls divided by the volume of the total unit cell. As we know from prior discussions, an atom is not a hard ball but mostly open space. However, the electrons orbiting around the nucleus do form a sphere of influence that, for the purposes of crystal structure discussions, can be approximated by a solid sphere. Thus, another name for FCC is cubic close packed.
Structure of solids
Published in Marios Soutsos, Peter Domone, Construction Materials, 2017
With the FCC structure, the coordination number is 12 (the atom in the centre of, say, the front face centre touches the eight corner atoms) and the close-packed direction is the face diagonal. From Figure 3.5, Each unit cell contains 8/8 + 6/2 = 4 atoms.Considering the close-packed direction gives 4r=√2aorr=√2a4∴APF=[4]×[(4/3π(√2a/4)3][a3]=0.74
Nanoporous Al sandwich foils using size effect of Al layer thickness during Cu/Al/Cu laminate rolling
Published in Philosophical Magazine, 2018
Hailiang Yu, Cheng Lu, A. Kiet Tieu, Huijun Li, Ajit Godbole, Charlie Kong
In Figure 5, it is seen that a number of pores have sidewalls characterised by 90° turns. This can be seen as the effect of the neighbouring grain orientation during deformation. The crystal structure of Al is face centred cubic (FCC) structure. The slip system of this type of material is {1 1 1} <1 1 0>, which is the root cause of the ductile plastic deformation and the formation of dimple shaped fracture surface during tensile testing of Al. However, the origin of the observed faceted pores with perpendicular sidewalls seems to be related to the cold work hardening and localised high stress concentration on some weak points along the grain boundaries within the deformed Al layer. This process may provide enough activation energy for nucleation of this type of pores along specific crystallographic orientations. The tensile stress on the exit side of rolling may enhance the displacement of material along the coalesced pores. Figure 8 shows that the longitudinal axis of an observed rectangular pore was found to be parallel to the [1 0 0] direction of the neighbouring grain. This implies that the sidewalls of the observed pore coincide with the {0 0 1} planes of this grain, which should not be associated with the transgranular dislocation glide on the slip system of {1 1 1} <1 1 0>. It is more likely for this type of faceted pores to be nucleated on the intergranular boundaries with the preferred crystallographic habit plane, such as {0 0 1}, and grow up to form the foam structure with the strong tensile stress during the rolling process. It is interesting to note that the phase interface between the Cu and the Al is much stronger than the internal intergranular structure of Al. This also directly leads to the formation of such a sandwich foam structure without signification defects on the binding region between the Cu and Al layers.
CO2 adsorption on the (111) surface of fcc-structure high entropy alloys
Published in Science and Technology of Advanced Materials: Methods, 2023
Adsorption sites in elementary substances are typically limited to high symmetry sites, such as top (or on-top), edge, and hollow sites. Hollow sites, where the atoms in each layer form a triangular lattice, can be divided into fcc and hcp sites. The layers in fcc {111} and hcp {0001} stack in ABCABC and ABABAB patterns, respectively. Therefore, when atoms in the topmost layer are in A positions and those in the next layer are in B positions, as in Figure 1(a,c), fcc and hcp sites are at C and B positions, respectively.