Strong body-centered cubic

The morphology of the ABA-type linear block copolymers is strongly influenced by the volume fraction of the two components. For example, in PS-EB-PS-type block copolymer as the volume fraction of PS is increased, the shape of the dispersed PS phase changes from spherical (comprising body-centered cubic spheres of PS dispersed in continuous soft phase) to cylindrical form (hexagonal packed cylinders of PS) [10,133,134]. When the volume fraction of the two phases... 

The spectrum of ethyne on Cu(110) at 280 K differs from those of ethyne on Ni(110) and Pd(110) at low temperatures in showing additional absorption bands and strong and well-defined vCC and vCH absorptions (56). Both of the latter bands are broad and weak for the other two metals. In the case of Fe(110), which has the different body-centered cubic (bcc) structure, the (110) plane is nearest to close-packed so that the observed type A spectrum at 120 K may have its more usual significance as indicating a four-metal-atom site not very different from that on fee (111) planes. Adsorption on Ag(110) at 100 K gives a spectrum much less strongly perturbed relative to the spectrum of the free ethyne molecule than any of the others. This clearly denotes relatively weak 77-bonding to the surface (57, 58), in marked contrast to the copper case. 

The transition metal carbides do have a notable drawback relative to engineering applications low ductility at room temperature. Below 1070 K, these materials fail in a brittle manner, while above this temperature they become ductile and deform plastically on multiple slip systems much like fee (face-centered-cubic) metals. This transition from brittle to ductile behavior is analogous to that of bee (body-centered-cubic) metals such as iron, and arises from the combination of the bee metals strongly temperature-dependent yield stress (oy) and relatively temperature-insensitive fracture stress.1 Brittle fracture is promoted below the ductile-to-brittle transition temperature because the stress required to fracture is lower than that required to move dislocations, oy. The opposite is true, however, above the transition temperature. 

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. 

PHYSICAL PROPERTIES steel-gray metallic pieces, powder, and flakes gray crystals blue-white hard metal body-centered cubic structure ductile odorless chromium (III) compounds are sparingly soluble in water chromium (IV) compounds are readily soluble in water soluble in acids (except nitric) and strong alkalis exists in active and passive forms Cr ion forms many coordination compounds MP (1890°C, 3434°F) BP (2672°C, 4841.6°F) DN (7.14 gW at 20°C) SG (7.14) ST (50 mN/m in air at MP) CP (5.58 cal/g-atom deg at 25°C) HV (81.7 kcal/g-atom) VD (7.1) VP (ImmHg at 1616°C). 

Besides semiconductor elements (e.g., silicon, carbon), there have been considerable efforts in the last several years devoted to the tight-binding modeling of metals. Since the strong directional d-band bonding in many body-centered cubic transition metals resembles the covalent bonding in semiconductors to some extent, they may provide good opportunities for TBMD approaches. 

The structure of bulk Na is body-centered-cubic. Consequently, the transition to the bulk structure has not yet occurred for N 20000, in the Na clusters formed in Martin s experiments. Alonso et al. [119] have proposed that the reason why the bcc phase is not yet formed at these large sizes is that the screening cloud, r (r), around a Na ion in a finite Na cluster depends so strongly on cluster size, that "( ) has not yet converged to its bulk limit even for clusters with ten thousand atoms. Since determines the effective... 

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