Pressure-induced structural transformation of clathrate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>Ge</mml:mi><mml:mn>136</mml:mn></mml:msub></mml:math> via ultrafast recrystallization of an amorphous intermediate

We study the pressure-induced structural transformation of ${\mathrm{Ge}}_{136}$ clathrate by ab initio molecular dynamics and metadynamics. The system under pressure first undergoes amorphization followed an ultrafast recrystallization to $\ensuremath{\beta}$-tin structure on time scale 30 ps. initial is triggered high while subsequent fast driven low temperature. Interestingly, amorphous intermediate still diffusive even at room temperature in spite very strong undercooling, making possible. provides explicit example between two crystalline phases proceeding via noncrystalline intermediate. On decompression with incipient order, blocked instead proceeds tetrahedral low-density (LDA) phase.