Electronic Properties and the Lattice Instability of Laves-Phase Zr<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">V</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Pure, perfect, single-crystal Zr${\mathrm{V}}_{2}$ does not undergo a structural phase transformation but all other sample modifications, including twinned single crystal, do transform (\ensuremath{\sim}100 K) from the cubic to a rhombohedral phase. All samples exhibit, in addition, an electronic instability (also \ensuremath{\sim}100 K). An anomaly in the ultrasonic velocity occurs at higher temperatures (\ensuremath{\sim}150-180 K) for pure polycrystalline Zr${\mathrm{V}}_{2}$ samples.