Abstract
A recent method for analysing the cohesion of transition metal carbides is applied to the carbides of tungsten. In the most interesting of these, WC, the W atoms are not close packed but are arranged in a simple hexagonal sub lattice of lower coordination number. It is proposed that this occurs so that the electrons of the W–W bonds can avoid the negatively charged C atoms more effectively than when in a carbide such as the NaCI type of the early transition metals. The ensuing stability of this WC structure exists, however, only so long as virtually all the C sites are full. When the C content drops appreciably below stoichiometric, separation into a two phase field occurs, consisting of stoichiometric WC and a lower carbide with a close packed metal sublattice.
MST/3092
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