Evidence of negative thermal expansion in supercooled tantala

A density anomaly, i.e. a temperature region with negative thermal expansion (NTE) bounded by maximum and minimum at lower temperatures, is revealed characterised in tantala for the first time Molecular Dynamics simulations. The NTE evidenced metastable supercooled liquid rather close to glass transition. Since suppressed poor structural equilibration, highlighting these phenomena highly challenging due need fulfilling competing constraints of slow cooling avoidance crystallization. We find that anomaly signalled decrease partial coordination numbers nTa,Ta nO,O when lowering temperature. magnitude comparable ones both stable water solid-state materials giant NTE.