Structure of the ordered compound V₆C₅

Accurate measurement of absolute experimental inelastic mean free paths and EELS differential cross-sections

“…The VC x was designated as having a high carbon content but no value of x was provided. Examination of selected area diffraction patterns showed ordering in good agreement with that found by Venables et al [33] showing that it is in the V 6 C 5 phase field of the phase diagram reported by Billingham et al [34]. This phase diagram shows that x could lie in the range 0.76 to 0.85 if the material had been allowed to equilibrate at ~600°C before cooling.…”

Disorder and Long‐Range Order in Non‐Stoichiometric Interstitial Compounds Transition Metal Carbides, Nitrides, and Oxides

“…6a). A successive helical displacement along the vectors {+, -4, l}, (4, -1, i}, and (1, -4, t} gives rise to a trigonal (space group P3,) V,C,-type structure [33] (Fig. 6b).…”

“…Studies of the ordering in a defective vanadium monocarbide, VC,, have revealed the existence of a trigonal high-temperature v6c5 modification [33] and a monoclinic lowtemperature [34, 351 V,C,-type modification, as well as a cubic V,V, modification with doubled (compared to the disordered carbide) lattice period [31, 361. Electron microdiffraction [34, 391 and neutron diffraction [15, 40 to 451 studies of the ordering in a non-stoichiometric niobium monocarbide, NbC,, have shown that annealing at temperatures below 1300 K leads to an ordered Nb,C, phase forming over a wide range of compositions near NbC,.,,. To describe the superstructure reflections observed, a trigonal structure similar to v&5 [33] has been proposed [34, 39, Niobium carbide specimens of different compositions within the region of homogeneity of niobium carbide were obtained [15] by solid-phase sintering of a mixture of powered metallic niobium and powdered acetylene black.…”

“…To describe the superstructure reflections observed, a trigonal structure similar to v&5 [33] has been proposed [34, 39, Niobium carbide specimens of different compositions within the region of homogeneity of niobium carbide were obtained [15] by solid-phase sintering of a mixture of powered metallic niobium and powdered acetylene black. The mixture was sintered at a temperature of 2300 K in a 0.001 Pa vacuum for 20 h, the product being intermediately ground every five hours of sintering.…”

Ab InitioStudy of Phase Equilibria inTiCx

“…As much as one-half of the carbon lattice sites can be vacant in the group IV and V transition metal carbides having the NaCl (B1) prototype crystal structure. Ordering of vacancies in some carbide systems, e.g., VC x , has been well established experimentally [2,3] and also studied theoretically [4].…”