Melting and pressure-induced amorphization of quartz

HIGH-PRESSURE CRYSTAL CHEMISTRY AND AMORPHIZATION OF e-QUARTZ

Single-crystal X-ray diffraction experiments on e-quartz at pressures to 15 GPa reveal structural instabilities that result in its gradual transition to an amorphous state. With increasing pressure the average Si-O distance ( ~ 1.61 + 0.01/~) and S i O 4 tetrahedral volume (,,~2.14 ___ 0.02.~ 3) remain constant. Compression of e-quartz results from a dramatic decrease in Si-O-Si angle and corre...

Pressure-induced structural evolution and amorphization in Eu3Ga5O12

A New Phase and Pressure Induced Amorphization in Silica

Using first principles variable cell shape molecular dynamics, we predict a new structure for silica. This structure results from annealing a-quartz at pressures near a major phonon instability. The new phase is obtained by rotations of SiO4 tetrahedra producing edge-sharing SiO6 octahedra and SiO5 cuboids. This type of mechanism was proposed to account for structural transitions in silicate me...

Atomic-scale mechanism for pressure-induced amorphization of b-eucryptite

We present here a reactive force field based metadynamics study of pressure-induced amorphization in b-eucryptite, a lithium aluminum silicate that exhibits negative thermal expansion, i.e., volumetric contraction upon heating. From our simulations, we found that b-eucryptite amorphizes under a moderate applied pressure of 3 GPa. A careful inspection of the amorphous phase showed that it contai...

Pressure-induced amorphization in the nanoindentation of single crystalline silicon

Large-scale molecular dynamics simulations of nanoindentation on a (100) oriented silicon surface were performed to investigate the mechanical behavior and phase transformation of single crystalline silicon. The direct crystalline-to-amorphous transformation is observed during the nanoindentation with a spherical indenter as long as the applied indentation strain or load is large enough. This a...