Crystalline-amorphous transition in silicate perovskites

Mahin Hemmati, Andrew Chizmeshya, George Wolf, Peter H. Poole, Jun Shao, Charles Angell

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

CaSiO3 and MgSiO3 perovskites are known to undergo solid-state crystal to amorphous transitions near ambient pressure when decompressed from their high-pressure stability fields. In order to elucidate the mechanistic aspects of this transition we have performed detailed molecular-dynamics simulations and lattice-dynamical calculations on model silicate perovskite systems using empirical rigid-ion pair potentials. In the simulations at low temperatures, the model perovskite systems transform under tension to a low-density glass composed of corner shared chains of tetrahedral silicon. The amorphization is initiated by a thermally activated step involving a soft polar optic mode in the perovskite phase at the Brillouin zone center. Progression of the system along this reaction coordinate triggers, in succession, multiple barrierless modes of instability ultimately producing a catastrophic decohesion of the lattice. An important intermediary along the reaction path is a crystalline phase where silicon is in a five-coordinate site and the alkaline-earth metal atom is in eightfold coordination. At the onset pressure, this transitory phase is itself dynamically unstable to a number of additional vibrational modes, the most relevant being those which result in transformation to a variety of tetrahedral chain silicate motifs. These results support the conjecture that stress-induced amorphization arises from the near simultaneous accessibility of multiple modes of instability in the highly metastable parent crystalline phase.

Original languageEnglish (US)
Pages (from-to)14841-14848
Number of pages8
JournalPhysical Review B
Volume51
Issue number21
DOIs
StatePublished - 1995

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Silicates
perovskites
Perovskite
silicates
Amorphization
Silicon
Crystalline materials
Alkaline Earth Metals
Alkaline earth metals
alkaline earth metals
silicon
Brillouin zones
progressions
Molecular dynamics
vibration mode
Optics
simulation
actuators
optics
Ions

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Crystalline-amorphous transition in silicate perovskites. / Hemmati, Mahin; Chizmeshya, Andrew; Wolf, George; Poole, Peter H.; Shao, Jun; Angell, Charles.

In: Physical Review B, Vol. 51, No. 21, 1995, p. 14841-14848.

Research output: Contribution to journalArticle

Hemmati, Mahin ; Chizmeshya, Andrew ; Wolf, George ; Poole, Peter H. ; Shao, Jun ; Angell, Charles. / Crystalline-amorphous transition in silicate perovskites. In: Physical Review B. 1995 ; Vol. 51, No. 21. pp. 14841-14848.
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