Understanding phase transitions of α-quartz under dynamic compression conditions - machine-learning driven atomistic simulations

Aug 5, 2026

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Machine-learning driven atomistic simulations are used to clarify how α-quartz transforms under shock compression, addressing inconsistent experimental claims about either amorphization or crystallization. A newly developed machine-learning interatomic potential models a peak pressure of 60 GPa over nanosecond timescales. The results show amorphization followed by recrystallization into defective d-NiAs-structured silica with silicon-sublattice disorder and partially ordered domains. By scanning strain conditions, the study identifies non-hydrostatic stress and strain states that enable diffusionless formation of rosiaite-structured silica.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages18

Reading Time45 min

AccessFree to download

Introduction

Geological shock effects and quartz relevance

Methods

Machine-learning interatomic potential and simulation setup

Results

Amorphization and recrystallization pathways

Diffusionless formation under non-hydrostatic strain

Background and prior models

Competing explanations for lamellar amorphization

High-pressure silica polymorphs

arXiv :2406 . 17676v1 [ cond-mat .mtrl-sci ] 25 Jun 2024 Understanding phase transitions of α-quartz under dynamic compression conditions by machine-learning driven atomistic simulations Linus C. Erhard, 1, ∗ Christoph Otzen,2 Jochen Rohrer, 1 Clemens Prescher,2 and Karsten Albe 1,† 1 Institute of Materials Science, Technische Universit¨at Darmstadt, Otto-Berndt-Strasse 3, D-64287 Darmstadt, Germany 2 Institute of Earth and Environmental Sciences, University of Freiburg, Hermann-Herder-Strasse 5, 79104 Freiburg, Germany Characteristic shock effects in silica serve as a key indicator of historical impacts at geological sites. Despite this geological significance, atomistic details of structural transformations under high pressure and shock compression remain poorly understood. This ambiguity is evidenced by conflicting experimental observations of both amorphization and crystallization transitions. Utilizing a newly developed machine-learning interatomic potential, we examine the response of α-quartz to shock compression with a peak pressure of 60 GPa over nano-second timescales. We initially observe amorphization before recrystallization into a d-NiAs-structured silica with disorder on the silicon sublattice, accompanied by the formation of domains with partial order of silicon. Investigating a variety of strain conditions enables us to identify the non-hydrostatic stress and strain states that allow the direct diffusionless formation of rosiaite-structured silica. Impacts of meteorites and asteroids on the Earth have contributed significantly to its geologic evolution and the development of life. Since the formation of the protoEarth through collisions of planetesimals in the early solar system [1] and the subsequent formation of the EarthMoon system through a giant impact [2], collisions have altered the surface of the Earth through, for example, the accumulation of water [3], sudden mass extinctions [4] and the creation of biological habitats [5] . The extreme pressure and temperature conditions during such impacts lead to specific alterations in the crystal structures of rock-forming minerals known as shock effects [6] . A special role can be ascribed to the mineral quartz, which is among the most common minerals of the Earth’s continental crust and thus affected by almost every continental impact. Its lamellar amorphization and transitions to high-pressure minerals can provide reliable evidences of past impacts and estimations of peak pressures [7] . For peak pressures between 10 and 35 GPa, planar deformation features occur in shocked quartz, which represent sets of amorphous lamellae with specific crystallographic orientations. While their frequency increase and dominant orientations vary for increasing shock pressures, quartz transforms completely to a diaplectic glass for peak pressures above 35 GPa. In contrast, the thermodynamically stable high-pressure phases stishovite and coesite occur only in trace quantities [8] . Transitions leading to the lamellar amorphization of quartz have previously been explained by different models. Early investigations suggested a direct transition to the amorphous state during shock compression [9–13], or the transition to the thermodynamically stable phasestishovite, which would then partially transform into an ∗ [erhard@mm.tu-darmstadt.de](erhard@mm.tu-darmstadt.de)[ ](erhard@mm.tu-darmstadt.de)† [albe@mm.tu-darmstadt.de](albe@mm.tu-darmstadt.de) amorphous solid and partially revert to quartz during decompression [14–17] . However, the lamellar amorphization of quartz was also discovered at static compression conditions [18, 19] . While spectroscopic studies suggested direct amorphization of quartz during compression above approximately 16 GPa [19–23], X-ray diffraction indicated transitions to one or several crystalline highpressure phases [24, 25] . A direct transition of quartz to stishovite has been excluded due to the large energy barrier associated to t

FAQs

What transformation sequence does the simulation show for α-quartz under shock compression?

It first exhibits amorphization, then recrystallizes into d-NiAs-structured silica with disorder on the silicon sublattice and domains with partial silicon order.

Which conditions determine whether rosiaite-structured silica forms diffusionlessly?

The study finds non-hydrostatic stress and strain states that enable direct diffusionless formation of rosiaite-structured silica.

Why are shock experiments difficult to compare with natural impacts?

Time-scale differences matter: natural impacts involve peak pressures and load durations on the order of milliseconds for small craters, unlike laboratory shock timescales.

Aug 5, 2026

Upload by Ezra