HCP hexagonal close

HCP = hexagonal close-packed FCC = face-centered cubic (cubic close-packed). i 0-300°C... 

Non Only (he three most common metallic structures arc listed hcp= hexagonal close-packed, bee = body-centered cubic, and fee = face-centered cubic values for the diamond structure will be discussed in Chapter 18. 

Dynamic Random Access Memory FeRAM = Ferroelectric Random Access Memory HCP = Hexagonal close packed HREM = High-resolution electron microscopy HTB = Hexagonal tungsten bronze MPTBh = Monophosphate tungsten bronzes with hexagonal tunnels MPTBp =... 

Lattice arrangements SC, simple cubic BCC, body-centered cubic FCC, face-centered cubic HCP, hexagonal close packing. 

Abbreviations BCC. body centered cubic DOS. density of states ESR. electron spin resonance HX.AI S, extended X-ray absorption fine structure F CC. face centered cubic (a crystal structure). FID, free induction decay FT, Fourier transform FWHM, full width at half maximum HCP, hexagonal close packed HOMO, highest occupied molecular orbital IR, Infrared or infrared spectroscopy LDOS, local density of states LUMO, lowest unoccupied molecular orbital MAS. magic angle spinning NMR. nuclear magnetic resonance PVP. poly(vinyl pyrrolidone) RF. Radiofrequency RT, room temperature SEDOR, spin echo double resonance Sf, sedor fraction SMSI, strong metal-support interaction TEM. transmission electron microscopy TOSS, total suppression of sidebands. 

Fig 2. Variation of cohesive energy with respect to atomic volume for various crystal structures. Atomic volume (V) is presented in ratio to atomic volume in equilibrium (Vq). Abbreviations on the picture are FCC face centred cubic, BCC body centred cubic, HCP hexagonal close-packed, DIA diamond, SC single cubic structures. 

HCP (hexagonal close packing) A type of crystal lattice structure found in zinc, titanium, and cobalt, for example. 

The three-dimensional computational grid contained 30 cells in the X direction, 28 cells in the Y direction, and 57 cells in the Z direction, each 0.004 cm on a side. The time increment was 8 x lO /rs. At the bottom of the grid was a reaction zone piston, which was programmed to initialize the flow with a steady-state reaction zone. After the steady-state reaction zone had traveled one reaction zone length in solid PBX-9404, it interacted with a two percent by volume HCP (hexagonal closed packed) matrix of air holes. 

Mg-Fe phase diagram calculated with the Pandat software [13] (BCC = body centred cubic, HCP = hexagonal close packed). 

The crystal stmcture of the most common phase. The acronyms for the crystal stmctures that appear in the Table stand for BCC = body-centered cubic, FCC = face-centered cubic, HCP = hexagonal-close-packed, GRA = graphite, TET = tetragonal, DIA = diamond, CUB = cubic, MCL = monoclinic, ORC = orthorhombic, RHL = rhombohedral. 

FCC = face-centered cubic HCP = hexagonal close-packed BCC = body-centered cubic. A nanometer (nm) equals 10 m to convert from nanometers to angstrom units (A), multiply the nanometer value by 10. 

CVN = Charpy V-notch (8.6) HCP = hexagonal close-packed crystal... 

Figure Bl.21.1. Atomic hard-ball models of low-Miller-index bulk-temiinated surfaces of simple metals with face-centred close-packed (fee), hexagonal close-packed (licp) and body-centred cubic (bcc) lattices (a) fee (lll)-(l X 1) (b)fcc(lO -(l X l) (c)fcc(110)-(l X 1) (d)hcp(0001)-(l x 1) (e) hcp(l0-10)-(l X 1), usually written as hcp(l010)-(l x 1) (f) bcc(l 10)-(1 x ]) (g) bcc(100)-(l x 1) and (li) bcc(l 11)-(1 x 1). The atomic spheres are drawn with radii that are smaller than touching-sphere radii, in order to give better depth views. The arrows are unit cell vectors. These figures were produced by the software program BALSAC [35]-...

Table 2.2 CALPHAD-type representation of the thermodynamic properties of face-centred cubic (FCC), liquid and hexagonal close-packed (HCP) aluminium of the form (after Dinsdale [18]) ...

Figure 2.12 6/ -G, (A1 FCC) of hexagonal closed-packed (HCP) aluminium and aluminium melt relative to that of face-centred cubic aluminium [18].

Most of the metallic elements of the Periodic Table crystallize in one or more of the highly symmetric structure types A1 (cubic close packed, ccp ), A2 (body-centered cubic, bcc) and A3 (hexagonal close packed, hcp) ... 

Figure 1.17 The extended unit cell of the hexagonal close-packed (HCP) structure.

A type of reconstruction that one might expect to occur but that has not been observed is related to the relatively easy phase transition between hep and fee metals this involves only the shifting of hexagonally close-packed layers of atoms, from the. .. ABABAB. .. to the. . . ABC ABC. . . stacking arrangement. Such a shift could easily occur for the topmost atomic layer of hcp(0001) or fcc(l 11) surfaces. Interestingly, it does not seem to take place in reality on the five hcp(OOOl) and nine fcc l 11) surfaces analyzed so far this includes the case of Co on both sides of its hep-fee phase transition. 

Fig. 2.54 Hexagonal close packing—relation between the hexagonal and ortho-hexagonal axes, (a) Hexagonal close packing projected on (OOI)hcp- (b) Relationship between the hexagonal (flh, hh, Ch) and ortho-hexagonal axes.

In general terms, transition metals are those which have incompletely filled d-bands. The progression in the filling of the d-band in the first long-transition metal series is as follows Ti(HCP), V(BCC), Cr(BCC), Fe(BCC), Co(FCC), Ni(FCC), Cu(FCC), Zn(HCP), and is not highly influenced by the structural difference between the body-centered cubic (BCC) and face-centered cubic (FCC) lattices. However, this is not the case for the hexagonal close-packed (HCP) lattice [10], An analogous pattern is expected for the second and third series. 

HBT HCP HDTV HEM heterojunction bipolar transistor hexagonal close packed high definition television heat exchanger method... 

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. 

A second type of boundary, in which there is no misorientation between grains, is the antiphase boundary. This occurs when wrong atoms are next to each other on the boundary plane. For example, with hexagonal close-packed (HCP) crystals, the sequence. .. ABABAB... can be reversed at the boundary to ABABA ABABA, where represents the boundary plane. Antiphase boundaries and stacking faults are typically of very low energy, comparable to that of a coherent twin boundary. 

Figure 3.1 shows each type of arrangement. In the first case, each sphere in the upper layer, of the set of three layers, is directly above one sphere in the lower layer. The spheres of the middle layer rest in the hollows between three spheres in each of the adjacent layers. There are two types of hollows in any close paced stmcture (vide infra) tetrahedral (a hole coordinated by four atoms) and octahedral (a hole coordinated by six atoms). The staggered close packed layers just described are sometimes represented as (... ABABAB...), where each letter corresponds to a two-dimensional closed-packed layer, and in which the sequence required to achieve three-dimensional close packing is clear. This is called hexagonal close packed and is abbreviated HCP. 

Of the 12 slip systems possessed by the CCP stmcture, five are independent, which satisfies the von Mises criterion. For this reason, and because of the multitude of active slip systems in polycrystalline CCP metals, they are the most ductile. Hexagonal close-packed metals contain just one close-packed layer, the (0 0 0 1) basal plane, and three distinct close-packed directions in this plane [I I 2 0], [2 I I 0], [I 2 I 0] as shown in Figure lO.Vh. Thus, there are only three easy glide primary slip systems in HCP metals, and only two of these are independent. Hence, HCP metals tend to have low... 

---