Monatomic glass formation through competing order balance

The phase transformation of single-element systems is a fundamental natural
process with broad implications, yet many aspects remain puzzling despite
their simplicity. For instance, transition metals, Tantalum (Ta) and Zirconium
(Zr), commonly form body-centred cubic crystals when supercooled. How
ever, according to large-scale computer simulations, their crystallisation rates
can differ by over 100 times. We reveal that this difference originates from
stronger competing ordering effects in Ta than Zr. The key thermodynamic
factor governing these kinetics is interfacial energy reduction through pre
ordering in a supercooled liquid state. In Ta, strong competition between
crystallisation and quasi-crystallisation occurs through non-classical pathways
facilitated by crystal-like preordering and hierarchical icosahedral ordering.
Conversely, Zr lacks this competing effect, leading to ultrafast crystallisation.
These distinct features influence their glass-forming ability, potentially
explaining the experimental synthesis of glassy Ta over other metals. Our
f
indings provide insights into the formation mechanisms of glasses, crystals,
and quasi-crystals of chemical elements.