Structural changes during a liquid-liquid transition in the deeply undercooled $\mathrm{Zr_{58.5}Cu_{15.6}Ni_{12.8}Al_{10.3}Nb_{2.8}}$ bulk metallic glass forming melt

Using high energy synchrotron x-ray radiation combined with electrostatic levitation, in situ structural analysisof a bulk metallic glass forming liquid is performed from above the liquidus temperature down to the glasstransition. The data indicate a liquid-liquid transition (LLT) in the deeply undercooled state at T /Tg ∼ 1.2 whichmanifests as a maximum in the heat capacity and an abrupt shift in the first peak position of the total structurefactor in the absence of a pronounced density change. Analysis of the corresponding real-space data showsthat the LLT involves changes in short- and medium-range order. The structural changes on the length scale ofmedium-range order imply a fragile-strong transition in agreement with experimental viscosity dat