Long-period order in vanadium carbide

Abstract

Periodic arrangements of anti-phase boundaries (APBs) have been detected by electron diffraction and microscopy in long-range ordered crystals of vanadium carbide near to the composition V ₆ C ₅, The APBs are non-conservative and are believed to accommodate excess vacancies or carbon atoms in response to deviations in crystal composition from V ₆ C ₅.

The atomic arrangement at non-conservative APBs has been deduced from diffraction contrast analysis of isolated APBs and their observed configurations in crystals containing non-periodic distributions. The observed variation in spacing of the long-periodic structure is consistent with analyses of the average crystal compositions. A mechanism of formation of the long-period structure has been deduced from observations on partially transformed crystals.