X-ray scattering study of temperature dependence of a structural incommensurability of the {omega} phase in Ti-V alloys

The incommensurate {omega} phase in titanium alloys has been revisited. A mechanism of the formation relevant to electron-lattice coupling has been re-investigated in terms of an x-ray-scattering technique on three kinds of single crystals, each containing 20, 24, and 27 mass % of vanadium respectively. The superlattice reflections of all systems observed for reduced wave vector q=(2/3+{delta},2/3+{delta},2/3+{delta}) at temperature congruent with 30 K reveal the following three effects for their intensity distribution with increasing temperature, where {delta} has a nonzero value giving the incommensurability: (1) decrease of the intensities (2) increase of the distribution widths, and (3) reduction of the {delta} values. The results suggest unstabilization of the lock-in state. A temperature region which indicates a notion of the transition is lowered with increasing concentration, implying excess of the valence electrons which prohibits lock-in nesting of the charge density wave. This idea was supported by molecular-orbital population analysis using cluster models of the two phases.